[A case of papillary cystadenoma of the epididymis]

We report a case of papillary cystadenoma of the right epididymis in a 48-year-old man. He consulted our hospital complaining of a small, painless mass at the upper pole of the right testis. There did not seem to be any remarkable problem of the mass. At 52 years old, the mass caused him pain, we diagnosed this case as chronic epididymitis, and performed right epididymectomy. On cut section, the tumor was multicystic and well encapsulated. The fluid within the cystic spaces was hemorrhagic. Microscopically, multimicrocysts were covered by tumor cells, which did not show any atypism or mitotic features. A papillary growth pattern was formed by vacuolated tumor cells around the capillaries in the microcysts, and a diagnosis of papillary cystadenoma of the epididymis was made. Papillary cystadenoma of the epididymis is considered a comparatively uncommon disease. To our knowledge, about 50 cases have been reported in the world literature, and this is the 17th case in Japan. Histologically, this tumor is similar in appearance to well-differentiated renal cell carcinoma, so it should be differentiated from metastatic renal cell carcinoma and multicystic papillary adenocarcinoma of the rete testis. The patient remains well with no evidence of recurrence or complication 8 months after excision. There is no evidence of renal cell carcinoma, nor features of von Hippel-Lindau's disease in this patient or his family.