Benign and malignant epithelial tumors of the rete testis in mice.

Two papillary cystadenomas and one papillary cystadenocarcinoma in the rete testis were found in two of 500 very old male JCL:ICR mice; the hosts had no other tumors. One mouse had bilateral cystic tumors. A 5 x 3 x 3 mm papillary cystadenoma was observed in the rete of the right testis. A 7 x 3 x 3 mm tumor with a mixed pattern of papillary cystadenocarcinoma and papillotubular adenocarcinoma was found in the rete of the left testis; the latter extended from the mediastinum to the ductuli efferents and the caput epididymis. The other mouse had a 9 x 5 x 5 mm papillary cystadenoma of borderline malignancy in the rete of the right testis. The mice had no clinical signs.