MIXED GERM CELL AND SEX CORD-STROMAL TUMORS IN DOG: CASE REPORT

Abstract

Testicular tumors are commonly described in canines, in which the sertolioma, seminoma and leydig cell tumor stand out. Mixed tumors are less frequent but may arise as an association among germ cells or between germ cells and interstitial cells. The aim of this paper is to describe a case of canine unilateral mixed testicular tumor, highlighting the pathological and immunohistochemical aspects. The case refers to a ten-year-old dog treated at Veterinary Hospital of the Federal University of Paraiba, Areia, Brazil, with a penile bleeding history for ten days. During clinical consultation, a volume increase in the left testis was observed, associated with moderate hematuria, which required the request for hematological examinations, abdominal ultrasonography and testicular cytology. Significant findings were observed only in testicular cytology, which were consistent with sertolioma. Given this condition, the animal was referred for surgery where both testicles were ablated and referred to the services of the Pathology Laboratory of the same institution for histopathological evaluation. Testicular fragments were fixed in 10% formaldehyde, routinely processed for paraffin blocks, cut in 3µm and stained with hematoxylin and eosin. Histopathological findings revealed contorted seminiferous tubules consisting of a proliferation of large cells, located perpendicular to the basal membrane of the tubules (Sertoli), with a broad and slightly granular cytoplasm of distinct boundaries, and nucleus with loose chromatin and unique and evident nucleoli. A second population was characterized pleomorphic interstitial cells proliferation, exhibiting large vacuolated cytoplasm and slightly eccentric nucleus (Leydig cells), with moderate anisocytosis and anisocariosis. Given this, the occurrence of a mixed testicular tumor was considered. For cell lineage confirmation, a tumor immunohistochemical study was requested, in which GATA-4, Melan A and alpha-inhibin were positive for leydig cells and PGP9.5 was positive for leydig and germ cells. Through immunohistochemical findings, mixed germ cell and stromal cord tumor was diagnosed, which differed from usual HE staining diagnosis. Testicular tumors are common neoplasms in canine species; however, they may occur with atypical morphological patterns, challenging the pathological diagnosis.