This 43-year old man presented with a testicular mass. Radical orchiectomy was performed.

The orchiectomy specimen revealed an intraparenchymal multicystic lesion with cysts measuring up to 2.5 cm in diameter. Many of the cysts were filled with chocolate-brown material. On microscopic examination, the cysts were lined by pseudostratified tall columnar epithelium (Fig. 9.1). The lining epithelial cells were flattened or cuboidal in some cysts (Fig. 9.2). The nuclei were enlarged and prominent nucleoli were readily apparent (Fig. 9.3). Many cysts had a prominent papillary component enclosing fibrovascular cores (Fig. 9.4, Fig. 9.5A & Fig. 9.5B) . The cysts were surrounded by peculiar spindle stroma. There was no evidence of stromal invasion. The non-neoplastic testicular parenchyma showed normal spermatogenesis. Immunostain for cytokeratin (AE1/AE3) was strongly positive (Fig. 9.6) and there was weak immunoreactivity for INHIBIN (Fig. 9.7).

The differential diagnosis includes mesothelioma (Fig. 9.8), carcinoma of rete testis (Fig. 9.9), serous papillary cystic tumor of borderline malignancy (Fig. 9.10), and teratoma (Fig. 9.11).

Serous Papillary Cystic Tumor of Testes

Key Features:

• Majority of ovarian-type epithelial tumors involving testes resemble ovarian serous tumors of borderline malignancy (low malignant potential). The lining epithelial cells show cytologic atypia; however there is no stromal invasion. Rare examples are associated with "destructive" stromal invasion with desmoplastic response warranting the diagnosis of serous carcinoma
• Other rare examples of ovarian-type epithelial tumors that have been reported in the testes include endometrioid adenocarcinoma, mucinous cystadenoma, mucinous cystadenocarcinoma, clear cell adenocarcinoma, and Brenner tumor
• Most serous papillary cystic tumors of testes occur in young adults. Testicular mass is the usual presentation
• Theories of origin of these tumors include: mullerian metaplasia of peritoneal lining of tunica vaginalis, origin from appendix testis, origin from mullerian remnants between testis and epididymis; some intratesticular mucinous tumors may represent monodermal teratomas
• Immunohistochemical profile of serous papillary carcinoma includes immunoreactivity for cytokeratin AE1/AE3, S-100, EMA, Ber-EP4, B72.3, and CEA; occasional cases are positive for PLAP and Vimentin
• The prognosis of borderline tumors is considered to be good; the presence of even microscopic areas of invasion increases the risk of distant metastases

1. Jones M, Young RH, Srigley JR, Scully RE. Paratesticular serous papillary carcinoma. A report of six cases. Am J Surg Pathol 1995; 19:1359-66.
2. Remmele W, Kaiserling E, Zerban U, et al. Serous papillary cystic tumor of borderline malignancy with focal carcinoma arising in testis: case report with immunohistochemical and ultrastructural observations. Hum Pathol 1992; 23:75-9.