Although large-cell
acanthoma is a well-known clinicopathological entity, its
biologic spectrum and nature are still subject to debate. We studied seven cases of large-cell
acanthoma by image analysis cytometry for
DNA content and by immunohistochemistry, using
antibodies to
proliferating cell nuclear antigen (
PCNA)/
cyclin. The data were compared with individual cases of
seborrheic keratosis (SK),
actinic keratosis (AK), and
Bowen's disease (BD). The
DNA distribution of large-cell
acanthoma was variable. There were varying peaks at the
DNA index values of 1 and 2 (diploid and
tetraploid values), but all cases contained a significant
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 diagnostic 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 all cases of large-cell
acanthoma. The discrepancy between the high number of
aneuploid and
tetraploid cells observed on the
DNA distribution curve and the lack of evidence for significant proliferation based on immunohistochemical stains suggest that these cells are resting cells with abnormal
DNA clone. Although these results provide additional information about the
biologic nature of large-cell
acanthoma, they do not resolve the controversial nosologic status of lesions in this histologic group.