Is isochromosome i(12p) present in gonadal precancerous tissue?

The development of frequent gonadal tumors in some syndromes of abnormal sexual differentiation is often preceded by carcinoma in situ. To detect possible early changes in chromosome number and/or structure associated with the carcinoma in situ, gonadal tissue was studied in one patient with the complete form of testicular feminization syndrome, two patients with the incomplete form of this syndrome, and one patient with Swyer's syndrome. In all patients aneuploidy with a bimodal distribution of chromosome numbers with the peaks at diploid and near-tetraploid values was shown. The possible specific chromosomal marker of gonadal tumors, isochromosome i(12p), has not been found. Its absence suggests that this marker might be associated with more advanced stages of long-term cancer development or it could be confined only to a subgroup of testicular tumors, as was proposed earlier. The hypothesis that the major source of hypotetraploid or near-triploid cells often found in many gonadal tumors might be endoreduplications with their subsequent chromosome loss is supported.