Testicular Teratoma And Seminoma In A Woodchuck

Abstract

Testicular teratomas are uncommon in domestic animals, occurring most frequently in the horse,' where they are found most often in retained testicle~,*.~.~ are considered benign, and may be single, multiple, unior bilateral, or c ~ s t i c . ~ Recently, a metastatic testicular teratocarcinoma was described in a 1%-year-old Foxtrotter horse.' To our knowledge, a testicular teratoma has not been previously described in a woodchuck. The present report details the occurrence of a concurrent teratoma and seminoma in the left testicle of a 4%-year-old woodchuck. At necropsy, the testicular neoplasms were considered incidental to the cause of death. The animal, maintained in a breeding colony, died of bacterial-induced severe pyogranulomatous necrotizing bronchopneumonia. The teratoma was composed of discrete to coalescing islands and thin sheets of well-differentiated squamous epithelial cells, some of which were forming keratin pearls (Fig. 1). Abutting these foci were dilated structures resembling hair follicles. These structures contained extensive keratin and debris. A focal zone of mature cartilage was adjacent to a dilated acinar-like structure lined by a predominantly low cuboidal epithelium (Fig. 2). A mature adipose tissue component was also present. The teratoma was partially surrounded and compressed by a monomorphic population of large polyhedral cells with scant acidophilic cytoplasm, and variably sized ovoid hyperchromatic nuclei with prominent nucleoli (Fig. 3). A diagnosis of seminoma was made. Neither neoplasm metastasized. Teratomas are composed of aberrantly located tissue elements from more than one germ cell layer.' In the present case, mature tissues of both ectodermal and mesodermal origin were present. Undifferentiated tissue was not seen. Testicular seminomas are occasionally seen in woodchucks (unpublished data). This is the first documented case of a testicular teratoma in a woodchuck.