Carcinoma in situ testis, the progenitor of testicular germ cell tumours: a clinical review.

Testicular germ cell tumours (TGCT), including seminomas, embryonal carcinomas, teratomas and yolk sac tumours, have a common precursor, the carcinoma in situ (CIS) cell. Recent gene expression studies displaying close similarity of CIS cells to embryonic stem cells support the longstanding theory that CIS most likely originates in utero from fetal gonocytes. The clinical association between the testicular dysgenesis syndrome components (TGCT, cryptorchidism, genital malformations, some forms of decreased spermatogenesis) also implies a prenatal origin. Despite high cure rates of TGCT, efforts should be made to obtain diagnosis at the CIS stage, as intervention is possible before an invasive tumour develops, thus reducing the necessity for intensive therapy. CIS may be suspected in patients with an assumed extragonadal GCT or cryptorchidism, and in intersex patients and selected cases with infertility (presenting with atrophic testes and ultrasonic microlithiasis). Surgical testicular biopsy seems the only reliable diagnostic method. The management of choice of unilateral CIS is orchidectomy, or localised irradiation in bilateral cases. At least 5% of TGCT patients present with contralateral CIS; therefore, contralateral biopsy is recommended at the time of orchidectomy. Further research is warranted to identify causal factors explaining the increasing incidence of TGCT and to obtain a method of non-invasive CIS detection.