Fluorescence in situ hybridization analysis of chromosome 12 anomalies in semen cells from patients with carcinoma in situ of the testis

Carcinoma in situ (CIS) of the testis is the precursor of seminomas and non-seminomatous germ cell tumours of the adult testis. A marked cytogenetic anomaly, the isochromosome of the short arm of chromosome 12 [i(12p)], has been demonstrated in over 80 per cent of all histological varieties of testicular germ cell tumours (TGCTs). In the remaining group of i(12p)-negative TGCTs, an overrepresentation of chromosome 12p sequences has been found. The i(12p) chromosome and overrepresentation of 12p sequences in CIS cells have also been reported. In order to establish whether numerical and/or structural aberrations of chromosome 12 can be found in CIS cells exfoliated into seminal fluid, semen specimens from ten patients with CIS lesions were investigated using bicolour double fluorescence in situ hybridization (FISH). The two DNA probes used, p alpha 12H8 and YAC 5, specifically detect the centromeric region of chromosome 12 and a subregion, p11.2-p12.1, on the short arm of chromosome 12, respectively. Ejaculates of ten azoospermic or oligozoospermic infertile males, presumably CIS-free, were used as negative controls. Nuclei exhibiting three or more chromosome 12 signals were found to be present in a significantly larger number in the patient samples than in the control samples. Nuclei with five or more chromosome 12 signals were observed in eight out of the ten patients. Morphologically similar arrangements to i(12p) were observed in some of the ejaculates. These results demonstrate the potential of FISH in the early detection of CIS and TGCTs in males at high risk.