Interphase-FISH examinations in paraffin sections from benign, precancerous, and cancerous lesions of the skin and oral mucosa.

In a preliminary pilot study centromeric probes for chromosomes #7, #8, #11, and #17 and two-colour-FISH were applied on interphase nuclei of 10 coded histologic thin sections obtained from archival paraffin material from precancerous lesions and malignant tumors of the mouth epithelium. Brilliant signals could be obtained in this material without any computerized processing. Among the ten coded probes, localized malignant areas within grade 2 leukoplakias could be detected by their increased number of aneusomic cells, as could the samples from carcinomas. In extension of this study archival paraffin material from 30 epithelial tumors of the skin were examined. The studied squamous cell and Bowen carcinomas were characterized by a large number of chromosomally aberrant subclones and gains of chromosomes were the prevailing finding. In contrast, keratoacanthomas showed distinctly less clonal variation, their majority exhibiting small, but significant clones with chromosome loss, particularly of chromosome #7, less distinctly of chromosome #17.