Chromosome analysis of three seminomas.

Each of three seminomas revealed chromosome #1 and #12 structural changes in direct preparations and short-term cultures. The #1 changes involved duplication of 1q and loss of 1p; in two, the breakpoint was in the heterochromatic region. The anomaly in #12 was a short arm isochromosome, usually present in duplicate. In one tumor, these were the only structural changes; in the other two, there was also involvement of #7, with extra copies of 7p. In one of these two tumors, a heterochromatic minute was identified after C-banding, and in the other, aside from two different markers containing part of #7, there was a dicentric derived from two chromosomes #15; this tumor proved to be prognostically unfavorable. Three normal chromosomes #1 and XXY sex chromosomes were present in each tumor. Chromosomes #11 and #13 were generally underrepresented, and #12 and #19-22 were over-represented.