The authors report a case of stage N3 pure testicular seminoma associated with paradoxical elevation of alphafoetoprotein (AFP). Despite the absence of histological arguments after review of the slides, this lesion was considered to be a stage pT1 N3 M0 S3 non seminomatous germ cell tumour with a poor prognosis. Simple surveillance was proposed following normalization of tumour markers, regression of retroperitoneal masses and negative PET scan. Laboratory and then clinical relapse at three months was treated by salvage chemotherapy followed by retroperitoneal lymph node dissection. The presence of embryonic carcinoma in one of the residual masses led to a revision of the initial histological diagnosis. The rare data of the literature indicate a variable approach according to alphafoetoprotein levels.