ESPRESSIONE DI MARKERS IMMUNOISTOCHIMICI IN GONADI NORMALI E PATOLOGICHE DI CANE

This study aimed to determine the immunophenotypical characterization of canine Sertoli cells (SCs) and related tumors and canine ovarian neoplasms. In veterinary literature histological and immunohistochemical aspects of canine Sertoli cell tumor (SCT) are poorly investigated and data on normal testes of mature and immature dogs are absent. In human medicine, numerous studies have shown that during maturation from fetal to adult testis, SCs undergo a process of differentiation whereby the expression of some markers is maintained, while other markers disappear and others are acquired. The comparison between the expression of cellular markers in normal and neoplastic testes may make clearer the temporal sequence of markers appearance in the dog, important for understanding the mechanisms underlying their re-expression in disorders of the adult testis. The analogies observed between canine and human species might clarify if the dog could be considered a good animal model for human testicular cancer. To evaluate the expression of Sertoli cell markers in normal and neoplastic canine testes, formalin fixed and paraffin embedded sections of testes from 2 fetuses, 15 newborns (from 0 to 20 days old), 5 puppies (from 43 days to 6 months old), 14 adult dogs and 21 canine SCTs (20 benign and 1 metastatic malignant SCT) were processed for histology and immunohistochemistry (ABC method) with antibodies against vimentin (1:1000), CKAE1/AE3 (1:3000), desmin (1:300), INH α (1:40) and AMH (1:30000). Histologically, 13/20 benign SCTs were classified as classical SCTs while 7/20, showing intracytoplasmic vacuoles, were considered “lipid rich”. The malignant SCT, largely necrotic, was composed of large cystic tubules lined by numerous layers of poorly-differentiated neoplastic SCs characterized by marked anisocytosis and anisokaryosis. The mitotic index of the SCTs ranged from 0 to1.6, with the highest value recorded in the malignant SCT. Immunohistologically, vimentin was always expressed by normal SCs from puppies and adults and by all SCTs taken in consideration. On the other hand, only 1 foetus and 4 newborns were positive immunolabelled. INH α was present exclusively in fetal and neonatal testes and in 13/21 SCTs, while desmin and CKAE1/AE3 were never present within normal testes but exclusively expressed by 7/21 and 5/21 SCTs, respectively. Finally, AMH was always expressed by foetal and neonatal testes, by the youngest puppies (43-45 days old) and by all the SCTs taken in consideration. We speculate that the expression of CKAE1/AE3, INH α, desmin and AMH observed in SCTs and not in mature testes may be a manifestation of de-differentiation. In fact, neoplastic SCs re-express foetal and neonatal makers, normally lost with maturation, demonstrating an immature phenotype. The re-expression of immunophenotypical markers of immaturity has been already described in several testicular pathologic conditions and the identification of the mechanisms via which this “cellular reversal maturation” occurs should be further investigated. Regarding ovarian canine epithelial tumours, given the variety of histological features that characterize this lesion and that can cause diagnostic difficulties or misinterpretation, the aim of this study was to investigate the reliability of the marker HBME-1 in canine normal ovaries, granulosa cell tumors, and epithelial ovarian neoplasms to determine whether this marker could be included in an immunohistochemical panel for differential diagnoses of canine ovarian tumors. Samples were obtained from 4 normal ovaries, 10 granulosa cell tumors, and 18 epithelial ovarian tumors. After formalin fixation and paraffin embedding, tissue sections were stained with hematoxylin and eosin and probed immunohistochemically for the HBME-1 marker. Granulosa cells and related tumors were consistently negative for HBME-1. Normal ovarian surface epithelium and 17 out of 18 ovarian epithelial tumors were positive for HBME-1. The results suggested that HBME-1 would be a useful marker for the differential diagnosis of ovarian tumors in the dog.