Traditionally, germ cell tumours (GCTs) have been classified based on their histological appearance, i.e. the differentiation of lineages. Various subtypes of seminomas have been identified in a number of classification systems, including anaplastic and spermatocytic seminoma. Here we present conclusive evidence that spermatocytic seminomas are GCTs with a separate pathogenesis from seminoma, and should therefore not be considered as a variant of seminoma. Moreover, the different putative animal models, either spontaneous or induced, are discussed in the context of their value as model for human GCTs. The canine seminomas are currently considered as the most informative model for human spermatocytic seminomas.