—  SPECIALTY CONFERENCE  —

Genitourinary Pathology

Case 3 - Carcinoma of Rete Testis

Isabel A. Sesterhenn
Armed Forces Institute of Pathology
Washington, DC


Click on each slide thumbnail image for an enlarged view
Clinical History:
This 58-year-old gentleman presented with a right testicular mass and bilateral hydroceles. A right orchiectomy was performed.


Case 3 - Figure 1 - Carcinoma of the rete. The tumor involves the rete testis and shows papillary, solid and tubular areas. H&E x 32.
Case 3 - Figure 2A - Transition from normal rete epithelium to tumor can be seen. H&E x 160
Case 3 - Figure 2B - Transition from normal rete epithelium to tumor can be seen. H&E x 160


Case 3 - Figure 3 - The infiltrating component consists of anaplastic cells with amphophilic cytoplasm and tubule formation. H&E x 160.
Case 3 - Figure 4A - Infiltrating tumor with focal tubule formation. H&E x 80.

MACROSCOPY
The testis measured 3x3.5x4 cm. On cut surface a necrotic multinodular tumor measuring 1.5x3.5x2.5 cm was seen. The epididymis and spermatic cord were unremarkable.

MICROSCOPY
The tumor involves the rete and infiltrates the adjacent testicular parenchyma as a mass consisting predominantly of tubules and cords. The cells are mostly amphophilic, but contain foci of glycogen rich pale cells. The tumor involving the rete shows tubules, papillary structures and solid areas. Transition from seemingly normal rete epithelium to the tumor is recognizable. The nuclei are anaplastic. Mitoses and extensive necrosis are present. The tumor infiltrates the interstitium with satellite deposits peripheral to the main tumor. There is a marked inflammatory infiltrate. There are psammoma bodies and in one focus, ossification. The tumor reacts with antibodies to cytokeratin, but is negative for calretinin.

Diagnosis: Carcinoma of rete testis

Discussion:
Tumors of the rete testis are rare and carcinomas are more common than adenomas. Most patients are in their sixties but the age range is from 20 to over 90 years. They present with a scrotal mass or pain. Inguinal hernia, hydroceles or symptoms similar to those of epididymitis may obscure the presence of the tumor. The duration of symptoms is variable but may extend over years.

Macroscopically, rete carcinomas are nonencapsulated masses, which may be greater than 10 cm in size. It is rarely cystic, unlike the rete adenomas.

Histologic criteria for the diagnosis of rete carcinoma include: a tumor involving and centered around the rete, transitions from normal rete epithelium to tumor epithelium, transitions from the tumor in the rete to the solid areas, and absence of a germ cell tumor. A primary tumor at another site, particularly a mesothelioma of the tunica vaginalis, should be ruled out. The tumor in the rete often has a tubular and papillary configuration and contains solid areas. It invades the testicular parenchyma in solid masses with or without tubule formation resembling Sertoli cell tumors. The tumor cells show nuclear anaplasia and have amphophilic cytoplasm. Mitoses can be identified. Necrosis is not uncommon. There may be psammoma bodies and even ossification.

Prognosis:
Carcinoma of the rete may infiltrate the epididymis and spreads to para-aortic, iliac and other lymph nodes and show hematogenous spread to visceral organs. Over 60% of patients develop metastasis, usually within a year. Treatment is usually surgery and chemotherapy. Radiotherapy appears to be of limited value.

Differential Diagnosis:
The differential diagnosis includes the rete adenoma, Müllerian-type tumors, particularly serous tumors of the testis, malignant mesothelioma and metastatic adenocarcinoma.

The rete adenoma is present exclusively in the lumina of the rete and often has a Sertoliform appearance. Another variant is that of a cystadenoma lined by cuboidal epithelium surrounded by fibrous stroma.

Serous tumors are usually located in the epididymal-testicular groove. Immunohistochemistry is helpful in distinguishing these tumors. The presence of intracellular mucin excludes the rete carcinoma.

Mesothelioma has to be excluded. These may invade into the rete but origin from the mesothelial lining of the tunica can usually be demonstrated.

Sertoli cell tumors are located in the testicular parenchyma and rarely extend into the rete.

Metastatic adenocarcinomas are usually a late event and part of generalized disease. The most common are prostatic and pulmonary origins and immunohistochemistry would be helpful in these cases.

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