Epididymal cribriform hyperplasia with nuclear atypia in p53 homozygous knockout mice on a mixed 129/Sv-FVB/N background.

: Epididymal cribriform hyperplasia (ECH) is a variant of normal epididymal histologic features in men, and has also been reported in rats, mice, dogs, cats, and bulls. The epididymal change has been associated with aging, testicular atrophy, cryptorchidism, and germ cell tumors. Epididymal cribriform hyperplasia was observed in p53 homozygous knockout mice on a mixed 129/Sv-FVB/N background, but not in wild-type or heterozygous mice. The aim of the study reported here was to determine the prevalence and characterize the morphologic, immunohistochemical, and ultrastructural features of ECH in these mice. Epididymal cribriform hyperplasia was present in 88% (72/82) of male mice ranging in age from seven to 65 weeks. The lesion was characterized microscopically by epithelial cells with atypical hyperchromatic nuclei, vacuolization, intratubular lumina formation, infrequent apoptosis, and rare mitotic figures. In contrast to germ cells, the cells of ECH did not express alpha-fetoprotein, carcinoembryonic antigen, or S-100. Ultrastructurally, the cells were pleomorphic with stereocilia at their apical borders and within intratubular lumina, and were supported by a basement membrane. Although 14% (10/72) of mice had concomitant testicular neoplasia, ECH did not appear to be a preneoplastic change. Investigators using these mice for modeling human disease should be aware of the background prevalence of this lesion.