Clinical and biological significance of carcinoma in situ of the testis

Carcinoma in situ (CIS) of the testis is a preinvasive lesion that with time progresses into invasive germ cell tumour. CIS precedes all types of germ cell tumours except spermatocytic seminoma. An increased risk of harbouring CIS has been reported in men with a history of cryptorchidism, in contralateral testes of men previously treated for unilateral germ cell tumour, in intersex patients, in men with assumed extragonadal germ cell tumour and possibly in infertile men. CIS develops into invasive germ cell cancer in 50% of untreated patients within five years of diagnosis, and it is believed that with time CIS will progress into germ cell cancer in almost all patients. A testicular biopsy is necessary to diagnose CIS. Cells with the characteristics of CIS cells have been detected in seminal fluid, and it may be possible to develop methods for diagnosing the condition by analysis of the semen. We recommend orchidectomy as the treatment of choice in cases of unilateral CIS, if the other testis has a potential for fertility. In other cases, such as patients with testicular tumour and CIS of the contralateral testis, we recommend localized irradiation of the testis with CIS. Leydig cell function seems to be slightly impaired, but sufficient for sexual function, after irradiation. CIS cells show morphological and immunohistochemical similarities with primordial germ cells (gonocytes), whereas they share only few features with spermatogonia. Therefore, we suggest that CIS cells are malignant cells derived from gonocytes during embryonic development.