Purpose: Keratoacanthoma (KA) is a rapidly growing cutaneous tumor and may be difficult to distinguish from squamous cell carcinoma (SCC) on histomorphology alone. There is a major controversy over the natural behavior of keratoacanthoma. KAs have been described as benign lesions, but also as variants of squamous cell carcinoma. It is important to distinguish these neoplasms because they have different clinical behavior and different therapeutic planning. The present study aims at investigating the role of P53, Ki67, and CD10 in differentiation between KA and SCC.

Patients and Methods: This retrospective study includes 18 cases of SCC, 12 cases of Keratoacanthoma, and 5 cases of normal skin as a control. Cases were collected from Pathology Department of Faculty of Medicine –Benha University, in the period 2010-2013. P53, Ki67, and CD10 immunohistochemical staining were performed in all cases and the pattern of expression was analyzed.
Results: 83.3% of the examined SCC cases and 41.7% of the examined KA cases showed nuclear expression of Ki-67 antigen and this was statistically significant (p