NO RECURRENT STRUCTURAL ABNORMALITIES APART FROM I(12P) IN PRIMARY GERM-CELL TUMORS OF THE ADULT TESTIS

Malignant transformation may be caused by gene deregulation resulting from specific chromosomal rearrangements, by amplification, by mutatio ns in proto-oncogenes, by loss of tumor suppressor genes, or a combina tion of these. We investigated the role of numerical and structural ch romosomal abnormalities in 102 cytogenetically abnormal cases of prima ry testicular germ cell tumors of adolescents and adults (TGCT) [32 se minomas (SE) and 70 nonseminomatous germ cell tumors (NS)]. We confirm ed that an isochromosome for 12p, i(12p), is the only consistent struc tural chromosomal abnormality in TGCT, present in about 70% of our cas es. Both the frequency and the number of copies of i(12p) are higher i n NS than in SE. This may suggest that i(12p) is involved in tumor pro gression. Besides i(12p), several clonal structural chromosomal abnorm alities were found, bur none appeared to be specific. SE and NS had ch romosome numbers in the triploid range, with significantly higher numb ers in SE than in NS (average modal chromosome number of 73.4 in SE an d 65.0 in NS). Both in SE and NS, some chromosomes were significantly underrepresented (e.g., 11, 13, 18, and Y) and others overrepresented (e.g., 7, 8, 12, 21, and X). In SE, a significantly higher copy number of chromosomes 7, 15, 19, and 22 was found and a significantly lower number of chromosome 17, compared with NS. These chromosomes may play an important role in the differentiation of TGCT. (C) 1995 Wiley-Liss, Inc.