—  SPECIALTY CONFERENCE  —

Cytopathology

Case 1 - Epithelioid Angiosarcoma

Lester J. Layfield, University of Utah, Salt Lake City, UT





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Clinical History
The patient is a 43 year old Iraqi American with a history of hypertension and hemophilia with Factor VIII deficiency. He has received numerous blood transfusions to help control his hemophilia. The patient is HIV positive secondary to multiple blood transfusions and also is known to be Hepatitis C positive. In May of 2009, the patient presented to Orthopedic Oncology Clinic with a large (20 cm) right thigh and hip mass. The mass was initially believed to be a massive hematoma based on his known history of hemophilia. Imaging studies including CT and MRI were equivocal for a neoplasm and a fine-needle aspiration was obtained. The FNA revealed rare atypical cells admixed with a large amount of blood. The patient underwent drainage and debulking of the suspected hematoma. Histologic evaluation of the specimen resulted in a diagnosis of malignancy. Following this diagnosis, the mass was resected. The patient was placed on chemotherapy and followed with CT examinations of the leg to detect possible recurrence as well as chest x-rays every three months. In October of 2011, multiple pulmonary nodules were detected as was an adrenal mass. Fine-needle aspiration of the adrenal mass was performed which yielded the material submitted for review.


Case 1 - Figure 1
Smear preparation showing a hypercellular area with many single cells and occasional small cell clusters. (Diff-Quik, x 200)
Case 1 - Figure 2
Single non-cohesive tumor cells with a polygonal shape. The nuclei are large and irregular. A single non-symmetrical mitotic figure is present. (Diff-Quik, x 200)
Case 1 - Figure 3
The individual neoplastic cells have moderate to abundant amounts of cytoplasm. The nuclei are eccentrically located and hyperchromatic often with large nucleoli. (Diff-Quik, x 400)
Case 1 - Figure 4
Cell block with tissue fragment composed of fibrous tissue surrounding groups of large epithelioid cells with abundant cytoplasm. (H&E, x 200)

Case 1 - Figure 5
Smear preparation containing a small cluster of tumor cells surrounding a clear lumen. (Diff-Quik, x 400)
Case 1 - Figure 6
Cell clusters composed of epithelioid and spindle-shaped cells. Many cells have a vacuolated cytoplasm. (Diff-Quik, x 600)
Case 1 - Figure 7
Oval to polygonal cells with large nuclei containing prominent nucleoli. Nuclei often have nuclear membrane irregularities. (Diff-Quik, x 1000)
Case 1 - Figure 8
Smear preparation containing occasional cells with atypical mitotic figures. (Diff-Quik, x 400)

Case 1 - Figure 9
Large tumor cells with multilobulated nuclear and large intracytoplasmic vacuoles. (Diff-Quik, x 1000)
Case 1 - Figure 10
Large mononuclear and binucleate tumor cells with abundant cytoplasm. (Diff-Quik, x 1000)
Case 1 - Figure 11
Large epithelioid cells some of which have vacuoles. The nuclei are often eccentrically located and have prominent nucleoli. (Diff-Quik, x 1000)
Case 1 - Figure 12
Multinucleated tumor giant cell. (Diff-Quik, x 1000)

Microscopic Findings:
Diff-Quik stained smears are of variable cellularity with areas of hypercellularity varying with paucicellular areas dominated by red blood cells. The dominate cell type is a large polygonal or epithelioid cell. These cells have moderate to abundant amounts of finely granular or vacuolated cytoplasm. The nuclei are large and hyperchromatic with generally oval nuclei which may lie eccentrically within the cell cytoplasm. Variability in nuclear size and shape is prominent with a minority of cells having a "spindle" shape. The majority of cells are non-cohesive and lie individually within the background. The nuclei contain prominent nucleoli or chromocenters. Nuclear membranes are often slightly irregular but folds and grooves are not a prominent feature. Nuclear cytoplasmic pseudoinclusions are not present. Occasional cells demonstrate erythrophagocytosis while others contain a golden-brown pigment. Mitotic figures including atypical forms are present. Occasional cell clusters are seen which may contain a central lumen. In most cases, the lumen is empty but occasionally contains one or two red blood cells. The background is dominated by red blood cells but in some areas contains necrotic cellular debris, fragments of disrupted cytoplasm and granules of golden-brown pigment.

Differential Diagnoses:
  1. Malignant melanoma

  2. Clear cell sarcoma of tendon sheath (melanoma of soft parts)

  3. Epithelioid sarcoma

  4. Metastatic adenocarcinoma

  5. Epithelioid angiosarcoma/epithelioid hemangioendothelioma

  6. High-grade plasma cell dyscrasia

  7. True histiocytic lymphoma

Final Diagnosis:
Epithelioid angiosarcoma.

Discussion:
Vascular neoplasms with an epithelioid morphology vary considerably in clinical behavior. These neoplasms vary in aggressiveness from the benign epithelioid hemangioma (histiocytoid hemangioma) to epithelioid hemangioendothelioma and epithelioid angiosarcoma. [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15] Histopathologic separation of these lesions into benign, intermediate and malignant forms is based on the presence or absence of cellular pleomorphism and architectural pattern. Recently, an apparently specific translocation has been identified in epithelioid hemangioendotheliomas. These neoplasms appear to be characterized by a non-random abnormality represented by t(1;3)(p36;3q25). [16]

Epithelioid hemangiomas and epithelioid angiomatous nodules pursue a benign course but the former may have considerable clinical and histologic overlap with Kimura's disease. [17] Kimura's disease is a chronic inflammatory condition most commonly seen in the Asian population. While initially confused with epithelioid hemangiomas, current data indicate that they are two entirely separate lesions with only a few superficial histologic similarities.

Intermediate and high-grade epithelioid vascular neoplasms are usually easily separable histologically from epithelioid hemangiomas. Epithelioid hemangioendotheliomas are characterized by a distinctive architecture with definitive angiocentricity and a myxohyaline or chondroid background. [4, 5, 8] The cells of epithelioid hemangioendothelioma are arranged in short cords or chains rather than surrounding vascular channels as seen in hemangiomas. Low-grade epithelioid hemangioendotheliomas are characterized by bland cells without mitotic activity. This aids in their distinction from epithelioid angiosarcomas. However, in approximately 20-25% of cases, the neoplastic cells of epithelioid hemangioendotheliomas will show significant nuclear atypia and mitotic activity. These tumors may also show focal spindling of the cells and/or necrosis. Such cases are difficult to separate from angiosarcomas as well as some examples of soft tissue metastases from carcinomas and melanomas. In distinction from epithelioid hemangioendotheliomas, epithelioid angiosarcomas are usually composed of solid sheets of highly atypical and mitotically active neoplastic epithelioid cells. Necrosis is a common finding in angiosarcomas. Vascular differentiation is demonstrated by the formation of irregular sinusoidal vascular channels and occasional cells showing intracytoplasmic lumen formation or small clusters of cells surrounding abortive lumens. [12, 13, 14, 15] Immunohistochemical demonstration of CD31 and CD34 expression is helpful in defining the endothelial direction of differentiation for both epithelioid hemangioendothelioma and epithelioid angiosarcoma. Unfortunately, some epithelioid vascular neoplasms express cytokeratins. [6] This complicates separation of these neoplasms from poorly differentiated metastatic adenocarcinomas.

The cytologic diagnosis of malignant spindle-cell vascular neoplasms (angiosarcomas and hemangioendotheliomas) can be challenging. The cytologic differential diagnosis of the epithelioid varieties of malignant vascular neoplasms appears even more complicated with a wide range of clinically significant differential diagnoses. Epithelioid hemangioendotheliomas and epithelioid angiosarcomas may be inseparable by purely cytologic evaluation. In general, however, epithelioid hemangioendotheliomas contain a cellular component with less nuclear atypia than is characteristic of epithelioid angiosarcomas.

Smear specimens obtained from epithelioid angiosarcomas have been reported to vary considerably in overall cellularity. [18, 19, 20, 21, 22] Liu and Layfield [22]reported low cellularity in their cases of epithelioid angiosarcoma. Minimo et al [18] reported smears obtained from epithelioid angiosarcomas to be highly cellular. In a large series of angiosarcomas reported by Klijanienko et al, [19] the majority of angiosarcomas were cell rich (59%). The presence of a hemorrhagic background is likewise variably present in published reports. Klijanienko found that only 31% of their cases were characterized by a hemorrhagic background. Minimo et al [18] and Liu and Layfield [22] reported that a hemorrhagic background was characteristic of epithelioid angiosarcomas. Other authors have also reported a prominent bloody background. [20, 21]

Cytologic features characteristic of epithelioid angiosarcoma include single neoplastic cells and small cell clusters, abortive vasoformative structures, papillary cell groups, rare intracytoplasmic red blood cells and a dominant population of neoplastic polygonal or epithelioid cells. [18, 19, 20, 21, 22] The cytoplasm may show vacuolations or lumina. [19] Nuclear atypia is of moderate to marked degree. In epithelioid forms of angiosarcoma, the cells are often grouped in clusters including papillary and gland-like groups. High power examination of the cells reveals the nuclei to have smooth membranes or membrane folds and irregularities. The cytoplasm stains dark blue in Diff-Quik preparations. Giant cells are seen in approximately a quarter of cases of epithelioid angiosarcoma. [19] Erythrophagocytosis is a common finding being present in approximately 40% of cases. Erythrophagocytosis occurs both in isolated cells and in cells forming clusters. Mitotic figures are found in only 20% of cases but may be of atypical form. Nucleoli are of variable character but are often large and multiple. [18]

Epithelioid angiosarcomas are high grade lesions and a large number of neoplasms must be considered in the differential diagnosis. Other epithelioid sarcomas must be considered including clear cell sarcomas of tendon sheath (melanoma of soft parts), epithelioid sarcomas, some rhabdomyosarcomas and alveolar soft part sarcomas. Because of the epithelioid appearance and cellular anaplasia, metastatic malignant melanoma must also be excluded. This is especially true when golden-brown to black pigment is present within some cells. Other significant considerations include metastatic poorly differentiated adenocarcinoma and metastatic renal cell carcinoma.

Epithelioid sarcomas enter the differential diagnosis of malignant epithelioid vascular neoplasms. Epithelioid sarcomas occur predominately in the extremities of young adults. These neoplasms have a histiocytic appearance often with an inflammatory background. Epithelioid sarcomas are characteristically keratin positive [18] but occasional angiosarcomas also express cytokeratins. [6] This can result in misdiagnosis of epithelioid angiosarcomas. However, the vacuolization and intracytoplasmic lumen formation seen within an epithelioid malignant vascular neoplasm aids in the exclusion of epithelioid sarcoma from the differential diagnosis. Additionally, the presence of hemosiderin in the background as well as phagocytized red blood cells supports the diagnosis of an epithelioid malignant vascular neoplasm (angiosarcoma).

Rhabdomyosarcomas may be confused with epithelioid angiosarcomas. Both may show marked variation in cell size and shape. Rhabdomyosarcomas are reactive with antibodies directed against muscle markers including desmin, caldesmin, myogenin and muscle specific actin. Rhabdomyosarcomas are non-reactive with antibodies directed against CD31 and CD34. Immunohistochemistry is of great aid in separating these lesions. Additionally, most rhabdomyosarcomas occur in the pediatric age group while epithelioid angiosarcomas are neoplasms of adults. Pleomorphic rhabdomyosarcomas are the most difficult to separate from epithelioid angiosarcomas but the presence of intracytoplasmic lumina and vacuolization of the cytoplasm favors the diagnosis of angiosarcoma.

Separation of epithelioid angiosarcomas from metastatic malignant melanoma and melanoma of soft parts is particularly difficult. Both neoplasms can present as cellular smears composed of both single cells and small cell clusters. Angiosarcomas and melanomas show marked nuclear atypia as well as intracytoplasmic and/or extracytoplasmic pigment. Melanomas frequently show intranuclear cytoplasmic pseudoinclusions and often greater degrees of nuclear irregularity than seen in epithelioid angiosarcomas. Moreover, malignant melanomas are immunoreactive with antibodies directed against S-100 protein, melan-A and HMB45. These markers are not expressed in epithelioid angiosarcomas. Also helpful in the separation of epithelioid angiosarcomas from malignant melanomas is the presence of intracytoplasmic lumina and small vasoformative structures in angiosarcomas.

Separation of epithelioid angiosarcomas from metastatic adenocarcinomas can be challenging. Both lesions may contain individual cells as well as small cell clusters. Similarly, both neoplasms may contain cells with intracytoplasmic vacuoles/lumina and may form small cell clusters with a central lumina or papillary fragments. Adenocarcinomas often form larger cell clusters or sheets which are not seen in epithelioid angiosarcomas. Special stains are also helpful in that adenocarcinomas may contain intra- or extracytoplasmic mucins which are absent from epithelioid angiosarcomas. Immunohistochemistry is helpful. While some angiosarcomas may express cytokeratins, [6] differential staining for cytokeratins including CK7, CK20, CK5/6 as well as epithelial membrane antigen may aid in establishing the presence of an adenocarcinoma. The immunoreactivity of the neoplastic cells for CD31, CD34 and FVIII-RA definitively demonstrates the endothelial direction of differentiation and establish the diagnosis of a vascular malignancy.

The cytologic recognition of epithelioid malignant vascular neoplasms can be challenging. These neoplasms are characterized by variable smear cellularity as well as a population of non-cohesive cells and cells forming small clusters. The presence of intracytoplasmic lumina occasionally containing red blood cells and small vasoformative cell clusters strongly suggests the diagnosis of epithelioid angiosarcoma. Immunohistochemical staining for CD31, CD34 and FVIII-RA is helpful in separating these malignancies from a variety of carcinomas, melanoma and other epithelioid sarcomas.

References
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