—  SHORT COURSE #49  —

Tumors of the Testis

Section 4 - Sex Cord-Stromal Tumors of Testis

John Srigley


Introduction
Sex cord-stromal tumors constitute about 4% of all testicular neoplasms, but account for approximately 8% of neoplasms in prepubertal males. These tumors are classified based on their resemblance to Sertoli, Leydig or non-specified stromal cells in the testis (table 1). Leydig cell tumors are the most common among the pure sex cord-stromal tumors, followed by Sertoli cell tumors, granulosa cell tumors and pure stromal tumors.

Table 1

Sertoli-stromal cell tumors
Sertoli cell tumor
Variants:
large cell calcifying
sclerosing
Sertoli-Leydig cell tumor
Leydig cell tumor
Granulosa-stromal cell tumors
Granulosa cell tumor
Variants:
adult
juvenile
Tumors in the fibroma-thecoma group
Mixed
Unclassified

Sertoli-Stromal Cell Tumors

Sertoli Cell Tumor
Sertoli cell tumors (SCT) account for about 1% of all testicular neoplasms. Historically, about one third of Sertoli cell tumors have been reported in children, although there is some controversy regarding these neoplasms. The majority of tumors reported as SCTs likely represent juvenile granulosa cell tumors. On rare occasion, SCTs develop in patients with androgen insensitivity syndrome and even more rarely arise in association with the Peutz-Jeghers syndrome. In those cases, patients may present with gynecomastia.

Gross Examination
SCTs have a wide size range with a mean diameter of 3.5 cm, but SCTs associated with the Peutz-Jeghers syndrome are usually smaller. SCTs are typically unilateral with the exception of tumors in patients with the Peutz-Jeghers syndrome and some large calcifying SCTs. The tumors are typically well circumscribed, frequently with a lobulated, yellow tan or white cut surface. Cysts may be present and sometimes prominent.

Microscopic Examination
At low-power magnification, the tumor shows nodular or diffuse patterns. Most SCTs, not otherwise specified, show sufficient tubular differentiation to allow the correct diagnosis. The tubules are hollow and round or solid and elongated but sometimes they may be quite irregular in size and shape and have a retiform pattern. A cord-like or solid growth may predominate in tumors with only focal tubular differentiation. The tubules are lined by a single layer of columnar or sometimes cuboidal cells with moderate to abundant eosinophilic cytoplasm, but the cytoplasm may be pale secondary to lipid accumulation. Sometimes, large vacuoles are present. The stroma may be scanty or abundant with prominent edema or hyalinization. Some tumors display marked sclerosis of the stroma encasing and distorting the tubular architecture (so-called sclerosing Sertoli cell tumor). These tumors are usually small. Most SCTs show minimal cytologic atypia and scant mitotic activity, but marked pleomorphism and brisk mitotic activity may be seen in malignant tumors.

Large Cell Calcifying Variant:
Occurs in patients from 2 to 51 years of age and is associated with Carney's syndrome and occasionally Peutz-Jeghers or androgen insensitivity syndromes. In syndromic cases, associated clinical findings include acromegaly, pituitary gigantism, hypercortisolemia, sexual precocity, spotty cutaneous pigmentation and sudden death. The pathologic findings consist of pituitary adenomas, bilateral primary adrenocortical hyperplasia, testicular Leydig cell tumors, cardiac myxomas and lentigines. Patients with Peutz-Jeghers syndrome have also elevated levels of estrogens and advanced bone age.

Gross Findings
Tumors are usually 4 cm or less (mean 2 cm), frequently multifocal and in 20% of cases bilateral. They have a firm, yellow to tan to white cut-surface with granular areas.

Microscopic Examination
The tumor cells grow in sheets, nests, trabeculae, cords and solid tubules. Intratubular tumor is found in approximately one half of the cases. The stroma may be loose and myxoid or extensively hyalinized. Many tumors have a neutrophilic infiltrate which may be useful in the differential diagnosis with other sex cord-stromal tumors. The calcification is usually conspicuous and sometimes very large, laminated calcific nodules are noted. Small psammoma bodies or areas of ossification may be seen. The tumor cells are large, rounded or polygonal with abundant eosinophilic, granular cytoplasm. The nuclei are round to oval with one or two small nucleoli. Ultrastructural studies support the origin from Sertoli cells with identification of Charcot-Böttcher filament bundles in some cases. Tumors occurring in males with the Peutz-Jeghers syndrome often have some features of large cell calcifying Sertoli cell tumor, but frequently lack calcification; in other cases they resemble the sex cord-stromal tumor with annular tubules of the ovary.

Prognosis
Most SCTs behave in a benign fashion. The percentage of malignant SCTs ranges between 10 to 22%. Malignant SCTs are rare in children. The most common site for metastases is the retroperitoneal lymph nodes, followed by mediastinal lymph nodes, lung, liver, bones and brain. In a recent study of 60 SCTs, not otherwise specified, conducted by Young and colleagues (1998), 7/60 SCTs (12%) were clinically malignant. Four patients had tumor spreading beyond the testis at the time of the diagnosis. Lymph node involvement was present in all of them with additional lung and bone metastases in one patient. Three additional patients developed metastases between 1.3 and 12 years after the diagnosis. In that study, features that correlated with a malignant clinical outcome included: (1) tumors > 5 cm in size, (2) necrosis, (3) moderate to severe nuclear atypia, (4) vascular invasion and (5) > 5 mitosis/10 high power fields. Five of the 7 malignant SCTs had at least three of those features.

The large calcifying variant of SCT may have a malignant course. Patients with malignant tumors are older (mean 30 years) than those with benign tumors (mean 17 years). Malignant tumors are typically unilateral and unifocal in contrast to the benign tumors that are multifocal and bilateral. Morphologic features that suggest a malignant course in the large cell variant of SCT are similar to those used for the conventional SCTs. The initial treatment for SCTs is orchidectomy. Retroperitoneal lymph node dissection is indicated in cases with radiographically evident retroperitoneal involvement.

Differential Diagnosis
The broad differential diagnosis includes non-neoplastic lesions such as Pick's adenoma as well as testicular neoplasms (granulosa cell tumor, Leydig cell tumor, seminoma, endometrioid adenocarcinoma), paratesticular tumors (adenomatoid tumor, sertoliform rete cystadenoma) and metastases. The most relevant are discussed below.

Sertoli Cell Nodule (so-called Pick's adenoma): These typically are microscopic non-neoplastic lesions, although they may be seen grossly as tiny white nodules. On microscopic examination, aggregates of closely clustered tubules with interspersed Leydig cells are seen. The tubules are lined by immature Sertoli cells and rarely contain spermatogonia. Intratubular laminated calcified bodies are occasionally present. This type of proliferation is typically seen in cryptorchid or undescended testes.

Granulosa Cell Tumor: Juvenile granulosa cell tumor has typically been confused with SCT. In contrast to SCT, juvenile granulosa cell tumor exhibits prominent follicles that are irregular in size and shape. If no follicular differentiation is present, the diagnosis of juvenile granulosa cell tumor can still be made with the finding of intercellular basophilic matrix imparting a chondroid appearance on the tumor. In contrast, SCTs usually display tubular differentiation. Juvenile granulosa cell tumor typically has more immature nuclei with conspicuous mitotic activity and importantly occurs in the first few months of life.

Leydig Cell Tumor (LCT): On gross examination, these tumors characteristically have a yellow to brown cut surface. At the histologic level, SCT may be confused with LCT, especially if it is associated with a diffuse growth of cells with abundant eosinophilic cytoplasm. The most helpful difference is the presence of tubular differentiation in SCTs.

Furthermore, almost half of LCTs contain crystals of Reinke. Immunohistochemical stains may be of relative help as cytokeratin shows much stronger and diffuse positivity in SCTs than in LCTs and in contrast, inhibin is much more intense and diffuse in LCTs. The large calcifying variant of SCT can be confused with a LCT, but the former shows tubular growth and they are commonly multifocal and bilateral. Calcification is not a feature of LCTs, however, extremely rare ossifying LCTs have been noted.

Seminoma: SCTs may have a diffuse growth pattern of cells with clear cytoplasm (secondary to lipid content) and have a non-specific chronic inflammatory infiltrate including lymphocytes resulting in a superficial resemblance to seminoma. Rarely seminomas may grow in a solid tubular pattern that at low-power suggests SCT. The presence of granulomas, rounded nuclei with "flattened" edges, one to four prominent nucleoli and glycogen content in the cytoplasm of the neoplastic cells will favor the diagnosis of seminoma. The finding of intratubular germ cell neoplasia and positive staining for glycogen, placental-like alkaline phosphatase and CD117 in seminoma and cytokeratin, inhibin and calretinin staining in SCTs are helpful in this differential diagnosis.

Unclassified Mixed Germ Cell Tumor: Sometimes sex cord-stromal tumors, more commonly SCTs or unclassified sex cord-stromal tumors, may incorporate germ cells but typically this occurs at the periphery and they are arranged in clusters, but occasionally they are in the center or have a diffuse distribution in the tumor. In most cases, these cells resemble spermatogonia and they do not stain for a variety of germ cell markers.

Sertoli-Leydig Cell Tumor
These tumors are rare and their histologic appearance is similar to that seen in their ovarian counterpart.

Gross Findings
They typically have a solid, yellow and often lobulated cut surface.

Microscopic Findings
Most tumors have tubules, cords and trabeculae in a haphazard arrangement in a background stroma that frequently contains Leydig cells. The majority of these tumors are of intermediate differentiation but rarely well differentiated, poorly differentiated tumors and tumors with retiform differentiation have been described. One of these tumors has been reported to contain osteosarcoma. The typical heterologous elements as seen in the ovary have not yet been reported.

Differential Diagnosis
The main differential diagnosis is with SCTs if the tumor shows prominent tubular differentiation. The presence of a cellular neoplastic stroma, sometimes with a Leydig cell component, is helpful in the diagnosis of Sertoli-Leydig cell tumor.

Leydig Cell Tumor
Leydig cell tumors (LCTs) account for 2-3% of all testicular neoplasms. They are the most common sex cord-stromal tumors. Approximately 20% are diagnosed during the first decade of life, 25% between 10 and 30 years, 30% between 30 and 50 years and 25% beyond 50 years. Clinically, patients typically present with a testicular mass but 15-30% of patients also develop gynecomastia. Other symptoms include decrease in libido or potency and children almost always present with isosexual pseudoprecocity owing to elaboration of androgens. Almost 10% of patients are asymptomatic and another 10% have undescended testis. Rare examples have occurred in patients with Klinefelter's or Turner's syndromes. The tumors typically produce testosterone, but secretion of other hormones has been reported. They can have high levels of estrogens and in those cases the levels of testosterone and follicle-stimulating hormone have been shown to be low. About 3% of these tumors are bilateral and 10-17% are malignant, the latter occurring only in adults.

Gross Findings
They are usually well circumscribed and range in size from 3 to 5 cm. They show a uniform solid, yellow to tan, although occasionally brown to brown-green cut surface. Lobulation is sometimes seen and areas of hemorrhage, necrosis or both are present in approximately 30% of the cases.

Microscopic Findings
LCTs commonly show diffuse or nodular growth patterns. In the latter, the stroma may be prominent and extensively hyalinized forming broad bands that subdivide the tumor in nodules. Occasionally, the stroma has a myxoid or edematous quality and the cells form regular nests, irregular clusters, trabeculae or cords. Adipose and osseous metaplasia has been described including the presence of psammomatous calcification. The cells are typically large and polygonal with abundant, slightly granular, eosinophilic cytoplasm. Cytoplasmic clearing is sometimes seen correlating with abundant lipids. Rare cases show spindle shaped cells forming ill defined fascicles as described by Ulbright and colleagues. Crystals of Reinke are identified in one third of cases and lipochrome pigment in 10-15% of cases. The nuclei are typically round and contain a single prominent nucleolus. Nuclear atypia is marked in 30% of tumors. Mitotic activity is low, but may be brisk in cases with marked atypia. Most cells containing fat in LCTs probably arise from lipid accumulation within the neoplastic Leydig cells and they stain for the same markers (inhibin, melan A) as typical Leydig cells but they also stain for S-100 indicating a hybrid phenotype. In the series reported by Ulbright and colleagues only 4/12 LCTs with adipose differentiation had fat of stromal derivation, either adipocytes or lipoblasts and the cells were negative for inhibin and melan-A and positive for S-100. Spindled areas when present do not seem to stain for Leydig cell markers.

Prognosis
In the largest series of LCTs of the testis conducted by Kim and colleagues, 5 of 30 patients with follow-up develop metastases (17%). Helpful features in predicting the behavior of these tumors include:
  • Older age. Patients with malignant tumors had a average age of 63 years compared to 40 years for patients with LCTs in general.

  • Larger size. In the series reported by Kim and colleagues, tumors larger than 6.9 cm were most likely to metastasize. Benign tumors average 2.7 cm.

  • Infiltrative margins and extension outside the testicular parenchyma.

  • Increased mitotic activity (> 3 mitosis/10 high power fields) and nuclear atypia.

  • Necrosis

  • Aneuploidy and high proliferative index. Cheville and colleagues found that all LCTs that metastasized were aneuploid. In contrast, only 38% of the non-metastasizing tumors were aneuploid by static image analysis. Furthermore, in the same study, malignant LCTs had a mean MIB-1 activity of 18.6% compared with 1.2% in non-metastasizing tumors.
Malignant LCTs typically spread to regional lymph nodes. Distant sites include lung, liver and bone. About 20% of patients with clinically malignant tumors have metastases at the time of initial diagnosis. The treatment requires orchidectomy and retroperitoneal lymph node dissection due to the high likelihood of lymph node involvement.

Differential Diagnosis
Leydig cell tumors may be confused with non-neoplastic and neoplastic lesions, the latter including SCT, yolk sac tumor, placental site trophoblastic tumor, lymphoma and metastases. The most relevant lesions are discussed here.

Leydig Cell Hyperplasia: This entity may represent a problem especially when it is florid as occurs in cryptorchid testes. Features that favor the diagnosis of Leydig cell hyperplasia include the lack of a discrete mass on gross examination and the presence of atrophic tubules intermixed with the lesion. Sometimes, Leydig cell hyperplasia is nodular and the presence of multiple nodules favors a hyperplasia over neoplasia.

Malakoplakia: It may form a single, homogeneous, yellow or brown mass grossly indistinguishable from a Leydig cell tumor. However, the presence of an abscess is a clue to the diagnosis of malakoplakia. Histiocytes with abundant eosinophilic cytoplasm may be confused with Leydig cells, however, the histiocytes are present in the interstitium as well as in the tubules and they are admixed with other inflammatory cells. The presence of Michaelis-Gutmann bodies is diagnostic of malakoplakia.

Testicular Tumor of the Adrenogenital System (TTAGS): TTAGS closely resembles LCT but is typically multifocal and bilateral. TTAGS have a darker brown color and seminiferous tubules are present within the lesion. The constituent cells tend to be larger than cells of LCT and have more abundant cytoplasm. They contain more abundant lipochrome pigment and lack crystals of Reinke. Thick fibrous bands separating cellular sheets is typical of TTAGS.

Similar nodules may be seen in patients with the Nelson's syndrome. Fat may be present in both TTAGS and LCT and for that reason is not helpful in the differential diagnosis.

Yolk Sac Tumor: When a LCT has abundant myxoid background and the cells contain cytoplasmic vacuoles, the tumor may be confused with a yolk sac tumor, more specifically with the microcystic pattern. The absence of other patterns typical of yolk sac tumor, the presence of typical areas of LCT, absence of a primitive appearance of the cells and low mitotic activity are helpful to make the diagnosis of LCT. Inhibin positivity, and AFP and cytokeratin negativity also help in the diagnosis of LCT versus yolk sac tumor.

Metastatic Carcinoma: Metastatic carcinoma , especially prostate cancer when there is a diffuse growth pattern may be confused with LCT. In such cases the clinical history is useful and at least focally one can usually identify characteristic prostatic glandular patterns. Immunohistochemical stains for prostate-specific acid phosphatase and prostate-specific antigen are also helpful. Another tumor in the differential diagnosis is malignant melanoma. Melanomas may have a diffuse or nodular growth pattern and cells with abundant eosinophilic cytoplasm. In general, the cells will show more nuclear atypia, mitotic activity and the clinical history will also be helpful. Immunohistochemical stains for HMB-45, S-100 and inhibin will be the most helpful in this differential diagnosis.

Granulosa-Stromal Cell Tumors

Granulosa cell tumors are subdivided in two major categories, adult and juvenile similar to their ovarian counterparts.

Adult Granulosa Cell Tumor
These are very rare tumors that occur in adult males with an average age of 42 years, the youngest patient reported to date was 16 years old. Patients may have a testicular mass for several years and/or gynecomastia.

Gross Findings
The tumors may be as large as 13 cm and typically they have a homogeneous, yellow-gray or white, firm and lobulated cut surface and cysts may be present.

Microscopic Findings
The appearance is similar to ovarian adult granulosa cell tumors with the more common patterns being diffuse and microfollicular with Call-Exner bodies. Other patterns may be found. The cells typically have scant cytoplasm and the nuclei are elongated with frequent grooves. The mitotic rate is generally low. The tumors may have a prominent fibromatous or fibrothecomatous background similar to that seen in ovarian counterparts. Immunohistochemical stains have shown that these tumors are positive for vimentin and negative for keratin.

Prognosis
Gross or microscopic features that have been associated with aggressive behavior are size greater than 7 cm, vascular or lymphatic invasion and hemorrhage or necrosis. Four patients with adult granulosa cell tumors have developed metastases. Two are alive, at 14 months and 14 years while the other two died of disease.

Differential Diagnosis
Unclassified Sex Cord-Stromal Tumor: These tumors may have an appearance similar to that of an adult granulosa cell tumor but only focally.

Juvenile Granulosa Cell Tumor
Juvenile granulosa cell tumor is the most common neoplasm of the testis during the first 6 months and almost all tumors are diagnosed during the first year of life. This tumor is occasionally seen in older children and rarely in adults. Approximately 20% of tumors occur in neonates with sex chromosome abnormalities affecting the Y chromosome and ambiguous genitalia (Drash syndrome), and nearly 40% occur in cryptorchid testes. In most cases, the tumors present as an asymptomatic scrotal mass with no associated endocrine manifestations. No malignant cases have been reported.

Gross Findings
The tumors measure up to 6.5 cm in largest dimension. They may be solid, cystic or both. The solid areas have a yellow-orange or tan-white cut surface and the cysts are thin and smooth.

Microscopic Findings
Solid, nodular or follicular patterns are the most common and sometimes alternate. The follicles vary from large and round to oval, to small and irregular. They contain basophilic or eosinophilic secretion that is mucicarmine positive. In the more solid or nodular areas, the cells grow in sheets or irregular clusters. The cells have moderate to large amounts of pale to eosinophilic cytoplasm, round to oval hyperchromatic nuclei, some of which contain nucleoli. Mitotic activity is usually brisk in contrast to the adult granulosa cell tumor. Some cases show extensive hyalinization in the form of nodules and may have a prominent myxoid background. The juvenile granulosa cells stain for cytokeratin and the neoplastic spindle cells between the cysts and solid nodules show smooth muscle differentiation with positivity for muscle-specific actin, smooth muscle actin and desmin.

Prognosis
Most patients undergo orchidectomy as the only treatment. No patients have developed recurrence or metastases.

Differential Diagnosis
Yolk Sac Tumor: Approximately 60% of testicular tumors occurring in infancy and childhood are of germ cell derivation, with yolk sac tumor accounting for almost two-thirds of the cases. However, in contrast to juvenile granulosa cell tumor, yolk sac tumor occurs in infants and children typically one year of age or older. From the microscopic point of view, the presence of irregular clusters of cells in a myxoid background showing brisk mitotic activity may cause confusion with a yolk sac tumor. The latter will have other typical protean microscopic patterns, more primitive cells that will stain for alpha-fetoprotein and will be negative for inhibin and calretinin.

Adult Granulosa Cell Tumor: These tumors also have a follicular growth pattern but the follicles tend to be larger, more regular and do not contain basophilic material. The nuclei are grooved and there is minimal mitotic activity. Finally, the age of the patient is also helpful as adult granulosa cell tumors occur in adult patients.

Sertoli Cell Tumor: See previous section.

Embryonal Rhabdomyosarcoma: This tumor may enter in the differential diagnosis because of the presence of relatively primitive nuclei, brisk mitotic activity, eosinophilic cytoplasm and follicles. However, embryonal rhabdomyosarcoma occurs in older children (mean 7 years), is typically paratesticular in location and some of the cells will show cross-striations. In difficult cases, immunohistochemical stains may be helpful (myoD1, myogenin and desmin).

Fibroma-Thecoma
These are uncommon tumors that resemble their ovarian counterpart, with thecomas being truly exceptional. They may be seen at any age (5 to 52 years) and patients present with a testicular mass.

Gross Findings
The tumors are variable in size but they are typically well circumscribed with a firm, white-tan to yellow cut surface.

Microscopic Findings
Fibroma-thecomas are composed of spindle shaped fibroblasts that grow in a storiform pattern in a background with variable amounts of collagen or edema. The tumors may be cellular as described in the ovary and may also have up to 2 mitotic figures/10 high power fields. Immunohistochemical results have shown that the cells stain for vimentin, actin and sometimes inhibin. They can also be focally positive for desmin, keratin and S-100.

Differential Diagnosis
Fibromatous Tumors of the Testicular Tunics: Both tumors may have a similar microscopic appearance although the tunical fibromas tend to be less cellular and generally lack inhibin staining.

Fibrosarcoma: There are no established criteria to differentiate these tumors, but the criteria used for the ovary can be applied here.

Sex Cord-Stromal Tumor, Unclassified: By definition, these tumors have at least focal epithelial differentiation, even though the fibromatous component is very prominent. It is important to separate both categories as all fibromas reported to date have been benign.

Leiomyoma: The cells in leiomyomas have more abundant eosinophilic cytoplasm and form larger fascicles.

Sex Cord-Stromal Tumors, Mixed and Unclassified
As it occurs in the ovary, sex cord-stromal tumors of the testis may be mixed. All the components should be recorded although the clinical behavior is most likely to be that of the prominent pattern or that in which the histologic appearance is most atypical.

Sex cord-stromal tumors unclassified are those that lack specific differentiation or contain patterns and cells resembling to varying degrees both testicular and ovarian elements. They occur at all ages and the most common clinical symptom is a painless testicular mass, although approximately 10% of patients have gynecomastia.

Gross Findings
These tumors are typically well circumscribed and they have a white to yellow, often lobulated cut surface that may be traversed by gray-white septa.

Microscopic Findings
In those tumors, a spectrum of patterns may be seen, ranging from predominantly epithelial to predominantly stromal. There frequently are solid or hollow tubules or cords with cells resembling Sertoli cells and islands or nodules of cells resembling granulosa cells in the better differentiated tumors, although the overall appearance of the tumor is not typical of a Sertoli or granulosa cell tumor. The stromal component is frequently fibromatous but may be densely cellular and may contain Leydig cells. If the tumor is less differentiated, it tends to exhibit more degree of nuclear atypia and mitotic activity. Diffuse and sarcomatoid patterns are commonly seen. Unclassified sex cord-stromal tumors often show positivity for S-100, muscle-specific actin and smooth muscle actin and some authors suggest a relationship to granulosa cell tumors.

Prognosis
It is important to note that these tumors are almost never malignant in children but they are malignant in approximately 25% of adult patients. Features that are associated with a malignant behavior include large size, extratesticular spread, necrosis, vascular invasion, marked nuclear atypia and brisk mitotic activity. If metastases are present, these are more frequently seen in lymph nodes but visceral dissemination is not rare.

Differential Diagnosis
The most problematic differential diagnosis is the distinction from all the pure sex cord-stromal tumors discussed earlier.

Immunohistochemistry
Sex cord-stromal tumors are positive for vimentin but this immunostain is not specific and for that reason not helpful in the diagnosis of these tumors. Keratin is frequently positive in Sertoli cell tumors, while the staining is focal or absent in Leydig cell and granulosa cell tumors and it is typically negative in fibromas. Epithelial membrane antigen (EMA) is typically negative in all these tumors but rare LCTs and SCTs have been reported positive. Commonly used immunohistochemical markers for sex cord-stromal tumors are as follows:

Inhibin: This is a 32-kDA heterodimeric glycoprotein hormone composed of a and b subunits. Inhibin is best known for its ability to suppress follicle-stimulating hormone. In men, the testis is the main source of inhibin, where it is secreted by Sertoli cells. Within the testis, inhibin is involved in the regulation of spermatogenesis as well as of steroidogenesis. In normal testis, inhibin stains Sertoli and Leydig cells as well as epididymis. In testicular sex cord-stromal tumors, inhibin positivity has been shown systematically in juvenile granulosa cell tumors, a very helpful finding to differentiate these tumors from yolk sac tumor. Leydig cell tumors also are consistently positive for inhibin even at metastatic sites. Sertoli cell tumors are not so uniformly positive for inhibin. In the series reported by Kommoss and colleagues only 30% of cases (6/20) were inhibin positive. McCluggage reported 28% positivity (2/7), in contrast to 91% positivity reported by Iczkowski (10/11). Occasionally, it may be morphologically difficult to distinguish between a SCT and a LCT. Because SCTs are inhibin negative in some cases, whereas LCTs are consistently positive, a lack of staining may be helpful in the differential diagnosis. As pointed out by McCluggage and colleagues, inhibin may be useful to distinguish LCTs from yolk sac tumor, as the former may have on occasion a microcystic pattern.

Calretinin: This is a 29-kilodalton calcium-binding protein of the calmodulin superfamily, acting as a buffer to prevent an abnormal intracellular calcium increase. It was originally discovered in neuronal tissue but subsequently found in mesothelial cells and in ovarian theca cells. In postpubertal testis, this antibody is expressed in Leydig cells but not in most Sertoli cells. In a very recent study using tissue microarray, Lugli and colleagues found consistent expression of calretinin in Leydig cells of the testis and strong and diffuse positivity in 5/5 Leydig cell tumors. Calretinin may be used if positive in the rare case of differential diagnosis of a Sertoli cell tumor from an adenomatoid tumor.

Melan A: This is an antigen recognized by cytotoxic T cells, mainly expressed in melanocytes. However, melan A has been found to be positive in 4 Leydig cell tumors of the testis in the study conducted by Busam and colleagues. This must be taken into account, especially in cases where the differential diagnosis may include melanoma metastatic to the testis. In those cases, S-100 and HMB-45 as well as a previous history of melanoma will be helpful in establishing the diagnosis.

CD99: The MIC-2 gene product is a reliable marker for Ewing's sarcoma and primitive neuroectodermal tumors. It is also expressed in normal Sertoli and granulosa cells and sex cord-stromal tumors of the ovary and testis. In the series reported by Kommoss and colleagues, CD99 was not as reliable a marker for sex cord-stromal tumors as inhibin. In that series, all but one CD99 positive tumors were also inhibin positive. Conversely, a number of inhibin positive tumors were CD99 negative.

S-100: In a recent study, Tanaka and co-workers have shown that normal Sertoli and Leydig cells and rete testis may stain for this antibody. In that study, all 8 SCTs of the large cell variant, conventional SCTs and LCTs were also positive.

Chromogranin: This antibody has been shown to be focally positive in non-neoplastic Sertoli and Leydig cells and in 82% of SCTs, 92% of benign LCTs and 43% of malignant LCTs in the series reported by Iczkowski and colleagues. However, in the series reported by Kommoss and colleagues, all sex cord-stromal tumors were negative for chromogranin.

References

General
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  19. Tetu B, Ro JY, Ayala AG. Large cell calcifying Sertoli cell tumor of the testis. A clinicopathologic, immunohistochemical and ultrastructural study of two cases. Am J Clin Pathol. 1991;96:717-22.

  20. Venara M, Rey R, Bergada I, Mendilaharzu H, et al. Sertoli cell proliferations of the infantile testis: an intratubular form of Sertoli cell tumor? Am J Surg Pathol. 2001;25:1237-44.

  21. White MD, Loughlin MW, Kallakury BV, Ross JS, et al. Bilateral large cell calcifying Sertoli cell tumor of the testis in a 7 year old boy. J Urol. 1997;158:1547-8.

  22. Young RH, Koelliker DD, Scully RE. Sertoli cell tumors of the testis, not otherwise specified: a clinicopathologic analysis of 60 cases. Am J Surg Pathol. 1998;22:709-21.

  23. Zukerberg LR, Young RH, Scully RE. Sclerosing Sertoli cell tumor of the testis. A report of 10 cases. Am J Surg Pathol. 1991;15:829-34.

Leydig Cell Tumor
  1. Billings SD, Roth LM, Ulbright TM. Microcystic Leydig cell tumors mimicking yolk sac tumor: a report of four cases. Am J Surg Pathol. 1999;23:546-51.

  2. Cheville JC, Sebo TJ, Lager DJ, Bostwick DG, Farrow GM. Leydig cell tumor of the testis: a clinicopathologic, DNA content and MIB-1 comparison of non-metastasizing and metastasizing tumors. Am J Surg Pathol. 1998;22:1361-7.

  3. Datta MW, Young RH. Malignant melanoma metastatic to the testis: a report of three cases with clinically significant manifestations. Int J Surg Pathol. 2000;8:49-57.

  4. Freeman A, Morris LS, Laskey R, Coleman N, Parkinson MC. Testicular Leydig cell tumors: prognostic value of proliferation markers. (abstract). Mod Pathol. 2003;14:108A.

  5. Gulbahce HE, Lindeland AT, Engel W, Lillemore TJ. Metastatic Leydig cell tumor with sarcomatoid differentiation. Arch Pathol Lab Med. 1999;123:1104-7.

  6. Hekimgil M, Altay B, Yakut BD, Soydan S, Ozyurt C, Killi R. Leydig cell tumor of the testis: comparison of histopathological and immunohistochemical features of three azoospermic cases and one malignant case. Pathol Int. 2001;51:792-6.

  7. Kim I, Young RH, Scully RE. Leydig cell tumors of the testis. A clinicopathological analysis of 40 cases and review of the literature. Am J Surg Pathol. 1985;9:177-92.

  8. McCluggage WG, Shanks JH, Arthur K, Banerjee SS. Cellular proliferation and nuclear ploidy assessments augment established prognostic factors in predicting malignancy in testicular Leydig cell tumors. Histopathology. 1998;33:361-8.

  9. Richmond I, Banerjee SS, Eyden BP, Sissons MC. Sarcomatoid Leydig cell tumor of testis. Histopathology. 1995;27:578-80.

  10. Rutgers JL, Young RH, Scully RE. The testicular "tumor" of the adrenogenital syndrome. A report of six cases and review of the literature on testicular masses in patients with adrenocortical disorders. Am J Surg Pathol. 1988;12:503-13.

  11. Ulbright TM, Srigley JR, Hatzianastassiou DK, Young RH. Leydig cell tumors of the testis with unusual features: adipose differentiation, calcification with ossification and spindle shaped tumor cells. Am J Surg Pathol. 2002;26:1424-33.

Granulosa Cell Tumor
  1. Al-Bozom IA, El-Faqih SR, Hassan SH, El0-Tiraifi AE, et al. Granulosa cell tumor of the adult type: a case report and review of the literature of a very rare testicular tumor. Arch Pathol Lab Med. 2000;1234:1525-8.

  2. Chan JK, Chan VS, Mak KL. Congenital juvenile granulosa cell tumor of the testis: report of a case showing extensive degenerative changes. Histopathology. 1990;17:75-80.

  3. Chan YF, Restall P, Kimble R. Juvenile granulosa cell tumor of the testis: report of two cases in newborns. J Pediatr Surg. 1997;32:752-3.

  4. Fagin R, Berbescu E, Landis S, Strumpf K, et al. Juvenile granulosa cell tumor of the testis. Urology. 2003;62:351.

  5. Jimenez-Quintero LP, Ro JY, Zavala-Pompa A, Amin MB, et al. Granulosa cell tumor of the adult testis: a clinicopathologic study of seven cases and a review of the literature. Hum Pathol. 1993;24:1120-5.

  6. Lawrence WD, Young RH, Scully RE. Juvenile granulosa cell tumor of the infantile testis. A report of 14 cases. Am J Surg Pathol. 1985;9:87-94.

  7. Matoska J, Ondrus D, Talerman A. Malignant granulosa cell tumor of the testis associated with gynecomastia and long survival. Cancer. 1992;69:1769-72.

  8. Nistal M, Redondo E, Paniagua R. Juvenile granulosa cell tumor of the testis. Arch Pathol Lab Med. 1988;112:1129-32

  9. Perez-Atayde AR, Joste N, Mulhern H. Juvenile granulosa cell tumor of the infantile testis. Evidence of a dual epithelial-smooth muscle differentiation. Am J Surg Pathol. 1996;20:72-9.

  10. Pinto MM. Juvenile granulosa cell tumor of the infant testis: case report with ultrastructural observations. Pediatar Pathol. 1985;4(3-4):277-89.

  11. Talerman A. Pure granulosa cell tumor of the testis. Report of a case and review of the literature. Appl Pathol. 1985;3:117-22.

  12. Young RH, Lawrence WD, Scully RE. Juvenile granulosa cell tumor-another neoplasm associated with abnormal chromosomes and ambiguous genitalia. A report of three cases. Am J Surg Pathol. 1985;9:737-43.

Fibroma:
  1. Allen PR, King AR, Sage MD, Sorrel VF. A benign gonadal stromal tumor of the testis of spindle fibroblastic type. Pathology 1990;22:227-9.

  2. Deveci MS, Deveci G, Onguru O, Kilciler M, Celasun B. Testicular (gonadal stromal) fibroma: case report and review of the literature. Pathol Int. 2002;52:326-30.

  3. Greco MA, Feiner HD, Theil KS, Muffarrij AA. Testicular stromal tumor with myofilaments: ultrastructural comparison with normal gonadal stroma. Hum Pathol 1984;15:228-43.

  4. Jones MA, Young RH, Scully RE. Benign fibromatous tumors of the testis and paratesticular region: a report of 9 cases with a proposed classification of fibromatous tumors and tumor-like lesions. Am J Surg Pathol 1997;7:47-53.

  5. Miettinen M, Salo J, Virtanen I. Testicular stromal tumor: ultrastructural, immunohistochemical and gel electrophoretic evidence of epithelial differentiation. Ultrastruct Pathol 1986;10:515-28.

  6. Weidner N. Myoid gonadal stromal tumor with epithelial differentiation (?testicular myoepithelioma). Ultrastruct Pathol 1991;15:409-16.

Sex Cord-Stromal Tumor, Unclassified
  1. Eble JN, Hull MT, Warfel KA, Donohue, JP. Malignant sex cord-stromal tumor of testis. J Urol 1984;131:546-50

  2. Renshaw AA, Gordon M, Corless CL. Immunohistochemistry of unclassified sex cord-stromal tumors of the testis with a predominance of spindle cells. Mod Pathol 1997;10:693-700.

  3. Ulbright TM, Srigley JR, Reuter VE, Wojno K, et al. Sex cord-stromal tumors of the testis with entrapped germ cells: a lesion mimicking unclassified mixed germ cell sex cord-stromal tumors. Am J Surg Pathol. 2000;24:535-42.

Immunohistochemistry
  1. Augusto D, Leteurtre E, De La Taille A, Gosselin B, Leroy X. Calretinin: a valuable marker of normal and neoplastic Leydig cells of the testis. Appl Immunohistochem Mol Morphol. 2002;10:159-62.

  2. Bertschy S, Genton CY, Gotzos V. Selective immunocytochemical localization of calretinin in the human ovary. Histochem Cell Biol. 1998;109:59-66

  3. Busam KJ, Iversen K, Coplan KA, et al. Immunoreactivity for A103, an antibody to melan-A (Mart-1), in adrenocortical and other steroid tumors. Am J Surg Pathol. 1998;22:57-63.

  4. Cao QJ, Jones JG, Li M. Expression of calretinin in human ovary, testis and ovarian sex cord-stromal tumors. Int J Gynecol Pathol. 2001;20:346-52.

  5. Deavers M, Malpica A, Liu J, Broaddus R, Silva E. Ovarian sex cord-stromal tumors: An immunohistochemical study including a comparison of calretinin and inhibin. Mod Pathol. 2003;16:584-90.

  6. Gordon MD, Corless C, Renshaw AA, Beckstead J. CD99, keratin and vimentin staining of sex cord-stromal tumors, normal ovary and testis. Mod Pathol. 1998;11:769-73.

  7. Hekimgil M, Altay B, Yakut BD, Soydan S, Ozyurt C, Killi R. Leydig cell tumor of the testis: comparison of histopathological and immunohistochemical features of three azoospermic cases and one malignant case. Pathol Inter 2001;51:792-6.

  8. Iczkowski KA, Bostwick DG, Roche PC, Cheville JC. Inhibin A is a sensitive and specific marker for testicular sex cord-stromal tumors. Mod Pathol. 1998;11:774-9.

  9. Kommoss F, Oliva E, Bittinger F, Kirkpatrick CJ, et al. Inhibin-alpha, CD99, HEA 125, PLAP and chromogranin immunoreactivity in testicular neoplasms and the androgen insensitivity syndrome. Hum Pathol. 2000;31:1055-61.

  10. Lugli A, Forster Y, Haas P, et al. Calretinin expression in human normal and neoplastic tissues: a tissue microarray analysis on 5233 tissue samples. Hum Pathol. 2003;34:994-1000.

  11. McCluggage WG, Shanks JH, Whitesidse C, Maxwell P, et al. Immunohistochemical study of testicular sex cord-stromal tumors, including staining with anti-inhibin antibody. Am J Surg Pathol. 1998;22:615-9.

  12. McLaren K, Thomson D. Localization of S-100 protein in a Leydig and Sertoli cell tumor of testis. Histopathology. 1989;15:649-52.

  13. Sasano H, Nakashima N, Matsuzaki O, Kato H, et al. Testicular sex cord-stromal lesions: immunohistochemical analysis of cytokeratin, vimentin and steroidogenic enzymes. Virchows Arch Pathol Anat Histopathol. 1992;421:163-9.

  14. Tanaka Y, Carney JA, Ijiri R, et al. Utility of immunostaining for S-100 protein subunits in gonadal sex cord-stromal tumors, with emphasis on the large cell calcifying Sertoli cell tumor of the testis. Hum Pathol. 2002;33:285-9.