Clear Cell Carcinomas of Müllerian Type and Rete Testis Origin Presenting as Scrotal Masses: A Study of Seven Cases

Ovarian-type epithelial tumors involving the testis and paratestis are rare, with clear cell carcinomas (CCC) one of the least frequent. We report our experience with 4 müllerian-type (MT) CCCs presenting as testicular/scrotal masses and arising in the paratestis (n=2) and seminal vesicle (n=2; well supported in 1 case and likely in the other). In addition, we document 3 cases of papillary CCC exclusively within the rete testis (RTCCC) and seminiferous tubules and differing from the MT tumors. The patients with MTCCC were 24 to 85 years old (median, 42 y), and 2 had metastases at presentation. The 2 originating in the paratestis were associated with other MT tumors, an endometrioid borderline tumor and a papillary serous borderline tumor. The other 2 MTCCCs likely involved the testis via extension from seminal vesicle primaries through the vasa deferentia. All MTCCCs showed typical features, including tubules, simple papillae with hyalinized cores, and solid nests of polygonal clear cells with occasional hobnail features. Both paratesticular primaries showed sarcomatoid foci with tumor-associated neutrophilic infiltrates. The 3 RTCCCs presented in 54-, 57-, and 60-year-old men as testicular masses; they showed intrarete arborizing papillary growth with nonhyalinized fibrous cores and piled-up, solid foci, lacked hobnail cells, and expressed carbonic anhydrase IX (2/2) and CD10 (2/2) but not CA125, unlike the MTCCCs. On follow-up, 2 patients with MTCCC died of metastatic tumor (4 and 13.5 mo), a third developed ileal and retroperitoneal metastases at 13 months; and the fourth died at 13.5 months of unspecified cause. Follow-up of 2 patients with RTCCCs showed 1 disease free at 8 months and another alive with unknown disease status at 13 years. We conclude that CCCs involving the testis may either be of MT with often aggressive courses or show some features of renal tumors, with confinement to the rete testis and indolent behavior.