Supernumerary chromosome 1 in interphase nuclei of atypical germ cells in paraffin-embedded human seminiferous tubules.

The so-called atypical germ cells or cells of carcinoma in situ morphologically resemble neoplastic cells in seminoma. Since seminomas show numerical aberrations of chromosome 1 we have used a DNA probe specific for chromosome region 1q12 to determine whether such aberrations can be detected in atypical germ cell nuclei in paraffin-embedded seminiferous tubules as well. One-third of intratubular nuclei, containing atypical germ cells, consistently showed three hybridization signals in contrast to two signals regularly observed in normal intestine and in spermatogonia. We thus show that cytogenetic studies of precancerous cells can be performed directly on the tissue where these cells originate.