How can one explain aneuploidy status in fibromatous and lipomatous naevus cell naevus?

34 lightly fibromatous, 23 heavily fibromatous, 5 lipomatous and 10 naevus cell naevi were stained with Feulgen kit in order to evaluate their ploidy status with CAS 200 image analyzer. 26/34 lightly fibromatous, 18/23 heavily fibromatous, and 5/5 lipomatous naevi were either suspicious for aneuploidy (Auer III) or clearly aneuploid (Auer IV). In contrast all 10/10 naevus cell naevi were euploid. Proliferation (S-phase) was not increased in naevi fibromatously and lipomatously changed. The mechanisms leading to aneuploidy are discussed.