LARGE-CELL ACANTHOMA OF THE SKIN - A STUDY BY IMAGE-ANALYSIS CYTOMETRY AND IMMUNOHISTOCHEMISTRY

Although large-cell acanthoma is a well-known clinicopathological enti ty, its biologic spectrum and nature are still subject to debate. We s tudied seven cases of large-cell acanthoma by image analysis cytometry for DNA content and by immunohistochemistry, using antibodies to prol iferating cell nuclear antigen (PCNA)/cyclin. The data were compared w ith individual cases of seborrheic keratosis (SK), actinic keratosis ( AK), and Bowen's disease (BD). The DNA distribution of large-cell acan thoma was variable. There were varying peaks at the DNA index values o f 1 and 2 (diploid and tetraploid values), but all cases contained a s ignificant aneuploid population between DNA index of 1 and 2. The mean DNA index was 1.44 (1.27-1.77); 1-20% of the cells exceeded 2, and 0- 2% exceeded 3. The DNA index for lesions in the other differential dia gnostic groups studied was as follows: SK, 1.0; AK, 1.4; BD, 1.8. The percentage of cells with positive nuclear staining for PCNA/cyclin was <20% in ail cases of large-cell acanthoma. The discrepancy between th e high number of aneuploid and tetraploid cells observed on the DNA di stribution curve and the lack of evidence for significant proliferatio n based on immunohistochemical stains suggest that these cells are res ting cells with abnormal DNA clone. Although these results provide add itional information about the biologic nature of large-cell acanthoma, they do not resolve the controversial nosologic status of lesions in this histologic group.