Proliferative Actinic Keratosis: An Invasive Squamous Cell Carcinoma or not?

Actinic keratoses have variants that differ clinically and pathologically. Proliferative actinic keratoses (PAK) are known to be resistant against standard therapies and to create a tendency for the development of invasive squamous cell carcinoma (SCC). This study retrospectively reviewed the medical records of 50 patients with 51 PAK lesions. Fifty patients (40 male, 10 female) with a mean age of 68.5 were included in the study. Thirty-two (63%) PAK lesions were clinically selected for total excision but only 27 of them could be totally excised. Among the excised lesions, 13 were reported to be PAK, 13 were SCC, and 1 was keratoacanthoma. There was no significant difference between the PAK and SCC groups. Overall, the groups with excised and unexcised lesions were statistically similar with respect to age, sex, lesion duration, localization, size, and surface features, but induration was more common in the SCC group. The mean follow-up time was 19.7 and 17.0 months in the PAK and SCC group, respectively. In conclusion, 25% (13/51) of lesions diagnosed as PAK were invasive SCC, which is of clinical and histopathological significance. Our results suggest that the definition of PAK should be histopathologically revised and that total excisional biopsy instead of punch biopsy should be considered, especially for lesions with a proliferative appearance.