[Correlation between electron microscopic nuclear irregularity index and malignancy of epidermal tumors]

Quantitative electron microscopy was used to measure nuclear contours of epidermal tumors. The degree of nuclear indentation in the epidermal cells, expressed as the nuclear irregularity index (NII), was calculated on electron micrographs by measuring the nuclear profile circumference and nuclear area. In all, 3,297 nuclei photographed from healthy skin specimens, seborrheic verruca, actinic keratosis (AK), keratoacanthoma (KA) and squamous cell carcinoma (SCC) were measured. Numbers and frequencies of special nuclei, which consisted of 2 nuclei or more and which had intranuclear cytoplasm, were also calculated. Significant differences were found between mean NII for SCC (1.376 +/- 0.258) and for healthy skin (1.236 +/- 0.152). In SCC, group mean NIIs for histologically high grade malignant cases and for recurrent and/or metastatic cases were higher than those of lower grade malignant cases and non recurrent metastatic cases. These findings suggest that NII can be regarded as a significant and objective marker for deciding the grade of malignancy and prognosis in SCC. KA also showed a high mean NII (1.328 +/- 0.215), but the frequency and types of special nuclei were different from those of SCC. In AK, the frequency of special nuclei was much higher than healthy skin, although no significant differences were found in mean NII.