Clonal heterogeneity in curetted human epidermal cancers and precancers analysed by flow cytometry and compared with...

DNA frequency distributions analysed by single nuclei flow cytometry were studied in sixty-five curetted human epidermal tumours, i.e. five actinic keratoses (AK), seven Bowen's diseases (BO), nine squamous cell carcinomas (SCC), forty-three basal cell carcinomas (BCC) and one baso-squamous carcinoma (BSC). Seventy-five per cent (16/21) of the samples with squamous cell differentiation (AK, BO and SCC) showed features suggestive of more than one stem cell population, against 24% of the pure BCC samples (11/43). The DNA indices for the tumours, i.e. the ratio between the DNA content of the tumour stem cell line G1 cells and normal epidermis G1 cells were calculated. For BCC and SCC a preponderance was found for near-diploid and near-tetraploid cell clones. The precancerous lesions contained clones with more broadly scattered DNA indices. The fractions of cells in S and G2M and S + G2M phases were calculated for the samples with only one detectable stem cell population. For the squamous cell tumours and the nodular (but not the superficial) BCC, these fractions were significantly different from the unaffected skin of patients with multiple epidermal cancers. The usefulness of cell cycle fraction determinations for curetted tumours is discussed.