DNA content and proliferative index in cutaneous squamous cell carcinoma and keratoacanthoma

The histologic separation of keratoacanthomas (KA) and well-differentiated squamous cell carcinoma (WDSCC) using established criteria may present a diagnostic dilemma in the individual case. The authors questioned whether the DNA index (DI) and/or the proliferative index (PI), as shown by flow cytometry (FCM) might assist in this differential diagnosis. Thirty-six well-differentiated squamous cell lesions of skin were independently classified as either WDSCC or KA by a panel of three pathologists. Six poorly differentiated squamous cell carcinomas (PDSCC) also were included in this study. Sections from paraffin blocks were prepared by standard techniques and analyzed by FCM. Mean DI values were: KA 0.96%, WDSCC 0.99%, and PDSCC 0.88%. The differences in the mean DIs were not statistically significant. Mean PI values were as follows: KA 16.7%, WDSCC 14.8%, and PDSCC 20.2%. Differences were not statistically significant. The authors conclude that the FCM measurements of DI and PI do not help in separating KA and WDSCC of skin.