Histopathological changes in testicular lesions in cats

ObjectivesThe aim of this retrospective study was to describe the neoplastic and non-neoplastic lesions seen on histopathological examination of cat testes in Hong Kong between 2018 and 2024.MethodsA total of 26 single or dual testes samples were collected from 18 cats by veterinarians at 14 veterinary clinics and submitted for histopathological examination. Laboratory records, including signalment, lesion location, age, breed and histopathological findings, were reviewed for each cat.ResultsNeoplastic testicular lesions were seen in three older cats (median age 8.5 years; range 3–17) compared with 18 non-neoplastic lesions in 15 cats (median age 1 year; range 0.5–3). The most common non-neoplastic lesions included inflammation (in the testes, epididymis, tunics and ductus deferens), cryptorchidism, and one case each of polyorchidism and epididymal cyst formation. Two of the testes with inflammation were identified on immunohistochemical staining as feline coronavirus-infected and one pair of testes was associated with the presence of extracellular Gram-negative bacteria at the lesion site. Three different neoplastic lesions were identified, one each of Sertoli cell tumour, leiomyoma and fibrosarcoma.Conclusions and relevanceNon-neoplastic testicular lesions were most common, including inflammation, cryptorchidism, polyorchidism and epididymal cysts. To our knowledge, leiomyoma and fibrosarcoma have not been reported in cat testes before and represent important differential diagnoses for testicular lesions.