Hair Sheath Keratins in Follicular Tumors: Identification in Keratoacanthoma and Their Significance as Differential Criteria from Squamous Cell Carcinoma

The study identified hair sheath keratins in three keratoacanthoma (KA) tumors using two-dimensional electrophoresis, revealing that KA is a follicular tumor at the cellular level. In a review of 17 KA cases over 13 years, significant histopathological features such as anagen keratinocytes, squamous eddies, trichilemmal keratinization (TK), and clear cells were observed. These features, particularly the presence of TK and small whirl structures, were found in nearly all tumors. The study concluded that examining follicular structures could serve as an important criterion for differentiating KA from squamous cell carcinoma (SCC), as distinguishing between the two can be challenging due to overlapping histopathological features.