Pseudoepitheliomatous hyperplasia in chronic cutaneous wounds. A flow cytometric study.

Cutaneous squamous cell carcinomas (SCC) arising in a setting of chronic regeneration and repair tend to be highly aggressive lesions prognostically distinct from SCC arising in solar-damaged skin. Full thickness thermal injury and chronic nonhealing ulcers are predisposing conditions in up to 2% of SCC. A significant association has been suggested to exist between pseudoepitheliomatous hyperplasia (PH) and SCC. Three-hundred-eighty-six surgical cases of skin excised secondary to severe burns (n = 254) or chronic ulcers (n = 132) were reviewed, yielding 43 (11%) with PH. Flow cytometric DNA analysis was performed on paraffin-embedded sections. Thirty cases without PH were studied in addition to the 43 cases with PH. The majority (39/43) of the PH cases showed a single diploid population with a mean S-phase of 13.7%. Four cases (9.3%) showed an aneuploid peak. All cases without PH were diploid with a mean S-phase of 9.0%. In this study, PH was present in 11% of cases reviewed, and showed a 50% mean higher S-phase than comparable cases without PH. Aneuploidy was present in 9.3% of the PH cases studied. SCC may arise from a subgroup of PH in a background of rapidly proliferating keratinocytes.