Bilateral mucinous cystadenocarcinoma of the testis and epididymis.

We describe an intratesticular mucinous cystadenocarcinoma in a 59-year-old man. The tumor was bilateral and appeared in the right testis and the left epididymis. The testicular tumor was a well-demarcated nodule, 3.5 cm in diameter, that extended from the lower testicular pole (close to the albuginea) to the epididymis compressing the corpus and infiltrating the cauda. The contralateral tumor, a 2.5-cm nodule located in the corpus epididymidis, compressed the ductus epididymidis. Both tumors consisted of multiple cavities varying in size, separated from one another by connective tissue septa that were incompletely lined by a columnar pseudostratified epithelium. The epithelial cells immunostained positively for carcinoembryonal antigen and comprised two cell types: cells showing a hyperchromatic nucleus, located in the basal portion of the cell, abundant rough endoplasmic reticulum, apical vacuoles, and numerous microvilli; and mucous cells. The cystic lumen showed a mucous content and sloughed epithelial cells. The differential diagnosis and histogenesis of these tumors is discussed.