The present study investigated the macroscopical and histological features of two spontaneous seminomas developed by zebrafish adults. Two wild-type male zebrafish of AB/TU strain aged 2 and 3 years, respectively, developed gross pathological signs consisting of asymmetrical swollen abdomens. In one fish, named fish 1, the testicular alteration is referred to as one testis (the right one), while in fish 2, both testes were alt...