A gain-of-function mutation in the KIT gene was first reported in human GCTs, including one ovarian dysgerminoma/yolk sac tumour by Tian et al. [10] and later studies have shown KIT mutations in a varying proportion of phenotypically indistinguishable testicular seminomas [12,14,15,36], primary mediastinal seminomas [11] and intracranial germinomas, both in males and females [13,17]. This evidence concerns the gene KIT and testicular seminoma.