X-chromatin, sex chromosomes, and ploidy in 37 germ cell tumors of the testis.

X-chromatin was present in interphase cells from nine of 14 teratomas and all of three combined tumors, but only one of 20 seminomas (which tended to have higher chromosome numbers). Eight of the 37 tumors were karyotyped; seven, only one of which (a teratoma) was X-chromatin-positive, had two X chromosomes while one, the X-chromatin-positive seminoma, had three. A possible relationship between the presence of inactive, X-chromatin-forming, X chromosomes and the number of autosomes is suggested by the data on the eight karyotyped tumors; the ratio of the number of Xs to the number of autosomes was higher for the two X-chromatin-positive tumors than for the remainder. All eight had at least one Y chromosome, and eight further tumors had one to three Y-bodies in their interphase cells. It is uncertain whether retention of the Y is a characteristic of male germ cell tumors, as tumors lacking a Y have been described by other workers. Two characteristics of these tumors, however, are high ploidy (at least 55 chromosomes), perhaps signifying an origin from a triploid or tetraploid cell, and chromosome 12 aberrations, usually resulting in an i(12p).