High chromosome numbers of seminomata and malignant teratomata of the testis: a review of data on 103 tumours.

Cytogenetic data on 103 seminomata and malignant teratomata of the testis from the literature and (partly in the form of DNA measurements) from this laboratory show that modal chromosome numbers are generally 50 or more. The only exceptions were 2 seminomata in which diploid and pseudodiploid karyotypes respectively were found, but the dividing cells may not have been tumour cells. Malignant tumours of the testis thus differ from those of all other sites (including the ovary) that have been studied sufficiently, where hypodiploid tumours are common. The reason for this difference is unknown. Mechanisms whereby high chromosome numbers, particularly the near-triploid numbers commonly found in testicular tumours, may be achieved are discussed briefly.