Vinclozolin induces an increase in leydig cell tumors in rats. Two mechanisms have been proposed linking PFOA to Leydig cell tumors. Leydig cells may grow uncontrollably and form a Leydig cell tumour. Puberty is the most common time for Leydig cell hypoplasia to be diagnosed. Immunohistochemical markers of Leydig cell tumours include inhibin-alpha, calretinin, and melan-A.