Proliferating Trichilemmal Tumor: Report of four cases

ABSTRACT

Proliferating trichilemmal tumor is relatively rare, and is generally considered to be a benign tumor that can be histologically mistaken for well-differentiated squamous cell carcinoma. The proliferating trichilemmal tumor is thought to be a tumor with differentiation toward the hair structure because the characteristic trichilemmal keratinization in this tumor is analogous to that of the outer root sheath of anagen hair or the trichilemmal sac surrounding catagen hair. We report four cases of proliferating trichilemmal tumor removed by surgical excision.