EN
Disorders of sex development (DSD) are rare in cats. They can be caused by chromosomal aberrations, gene mutations or other undefined factors. The aim of the present study was to compare the histological structure and immunohistochemical reactivity of testes in cats with DSD and in healthy cats. The research material consisted of the gonads of four cats – phenotypic males with an incorrect structure of the reproductive system. The control group consisted of the testes of four healthy cats – routinely castrated phenotypical males. The material was fixed with formalin and embedded in paraffin; the sections were stained with hematoxylin and eosin. The immunohistochemical investigation were performed using monoclonal and polyclonal antibodies directed against desmin, vimentin, actin of smooth muscles, S100 protein and MCM3 protein. The results obtained allow concluding that the testes of cats with DSD differed in certain respects, mainly in the number of blood vessels, from the normal testes. Moreover, the results of immunohistochemical examination indicate that in the testes of cats with DSD the number of supporting cells is lower, the amount of interstitial cells is comparable and spermatogenesis is correct es compared to those determined in the control gonads. The number of blood vessels in cats with DSD is reduced by about 30%. It confirms the recommendations for castration of these animals in order to eliminate the potential inheritance of sex development disorders.