The nuclear DNA content characterization was carried out by means of b
oth DNA index and DNA histogram type assessments in a series of 21 ret
inoblastomas, 11 neuroblastomas, 1 ganglioneuroblastoma, and 4 medullo
blastomas. These measurements were performed by means of the cytophoto
metric digital cell image analyses of Feulgen-stained nuclei. The resu
lts indicate that as far as nuclear DNA content is concerned, retinobl
astomas seem to be very different from neuroblastomas. In fact, in ter
ms of DNA index, retinoblastomas are significantly more aneuploid than
neuroblastomas. The DNA histogram type shows that the high level of a
neuploidy found in retinoblastomas corresponds to genotypically polymo
rphic tumors, and this could reflect a serious degeneration of the gen
omic material in retinoblastomas. This type of degeneration seems to b
e much less frequent in neuroblastomas, which basically seem to be eit
her diploid or hypertriploid.