Adenomatous hyperplasia of the rete testis. A clinicopathologic study of nine cases.

Adenomatous hyperplasia of the rete testis is an uncommon lesion that has recently been described. Nine cases of adenomatous hyperplasia were identified in two institutions from 1980 to 1989. At diagnosis the nine patients ranged in age from 30 to 74 years (mean, 59 years; median, 66 years). Three patients presented with a grossly identifiable solid or cystic testicular hilar mass. In six cases adenomatous hyperplasia was an incidental microscopic finding--five from orchiectomy specimens and one from an autopsy specimen. Microscopically, the hyperplasia consisted of a tubulopapillary epithelial proliferation of rete testis. The lining cells were cuboidal to low columnar and lacked nuclear pleomorphism or mitotic figures. The involvement of the rete testis was predominantly diffuse. In seven cases the seminiferous tubules showed atrophic changes. Ultrastructural and immunohistochemical (keratin, epithelial-membrane antigen: positive; vimentin, muscle-specific actin, desmin, and S-100: negative) studies done on one case showed similar features to those of nonhyperplastic rete testis epithelium. No patient with adenomatous hyperplasia showed local recurrence or metastasis. Possible pathogeneses include hormonal imbalance or stimulatory influence that remains as yet unidentified.