Epididymal Interstitial (Leydig) Cell Tumors in B6C3F₁ Mice

Abstract

Abstract. Six primary interstitial cell tumors of the epididymis were identified from 46,752 male B6C3F, mice used in chronic toxicity and carcinogenicity studies. Five of the tumors occurred at the end of 2-year studies; none were attributed to treatment. None of the mice with epididymal tumors had a primary testicular tumor. Histologically, tumors were characterized by a nodular or diffuse proliferation of tumor cells in the epididymal interstitium. Most cells were polygonal with highly vacuolated cytoplasm (vacuolated cells) or eosinophilic cytoplasm (eosinophilic cells). Smaller hyperchromatic cells with scant basophilic cytoplasm (basophilic cells) and cells with yellow-brown pigment characteristic of lipofuscin (pigmented cells) were less common. In each tumor two or more cell types were present. Extension of these tumors through the capsule, invasion of the testis, or metastasis did not occur. By electron microscopy both eosinophilic and vacuolated cell types had a large round or oval nucleus with sparse heterochromatin, abundant mitochondria with tubulovesicular cristae, and frequent desmosome structures between cell membranes. Vacuolated cells contained numerous lipid droplets. Morphological features of the epididymal tumors are similar to those of the testicular interstitial (Leydig) cell tumor in mice and rats.

Proliferative and Nonproliferative Lesions of the Rat and Mouse Male Reproductive System

“…Comments: Rare tumor described in B6C3F1 mice (Mitsumori et al 1989; Mitsumori and Elwell 1988). There are no reports on epididymal Leydig cell hyperplasia or carcinomas, and since Leydig cells normally are not found in the epididymis, it has been suggested that these tumors may in fact be primary histiocytic sarcomas of the epididymis (Yano et al 2008).…”

“…Two tumor types specific to the epididymis have been described in the mouse; these are histiocytic sarcoma and Leydig cell adenoma. (Mitsumori et al 1989;Mitsumori and Elwell 1988). There are no reports on epididymal Leydig cell hyperplasia or carcinomas, and since Leydig cells normally are not found in the epididymis, it has been suggested that these tumors may in fact be primary histiocytic sarcomas of the epididymis (Yano et al 2008 There is some suggestion that lesions diagnosed as Leydig cell tumors may in fact be histiocytic sarcomas (Yano et al 2008).…”

Mixed testicular neoplasia in a short beaked common dolphin Delphinus delphis

“…A few reports of testicular neoplasia in other species as ferrets and rabbits exist (IrizarryRovira et al 2008, Batista-Arteaga et al 2011. In laboratory animals, an interstitial (Leydig) cell tumor in mice and a mixed Sertoli-Leydig cell tumor in rats have been described (Rehm & Waalkes 1988, Mitsumori et al 1989.…”