RESUMO
Proliferating trichilemmal cyst(PTC) is a rare benign neoplasm that is thought to be derived from the outer root sheath of anagen hair follicles differentiating toward the infundibular and matrical segments, sebaceous glands, apocrine glands, or acrosyringium. Clinically, it presents as a solitary elevated, lobulated mass on the scalp of elderly women. Histologically, it shows well demarcated multiple lobules of squamous epithelium. The center of the lobule undergoes abrupt keratinization without formation of keratohyalin and foci of calcification are often present in the areas of amorphous keratin. PTC can be associated with sebaceous nevus of Jadassohn, ectopic apocrine sweat glands, spindle cell carcinoma, etc. We report an unusual case of proliferating trichilemmal cyst with trichoepitheliomatous change in a young woman.