A Case of Trichilemmal Cyst of the Finger

Choi, Chang Min; Cho, Hee Ryung; Lew, Bark Lynn; Sim, Woo Young

Abstract

Trichilemmal cysts are cysts of epithelial origin with a distinctive keratinization pattern that simulates that of the human anagen hair follicle between bulge and sebaceous gland and in the sac surrounding catagen hairs. This type of keratinization of the outer root sheath epithelium occurs when it is freed from the internal cover of its inner root sheath. Over 90 percent of trichilemmal cysts occur on the scalp. The others are located on the face, neck and trunk. A 34-year-old female had a solitary, skin-colored nontender subcutaneous nodule on the 5th finger of her right hand. We clinically diagnosed this skin lesion as an epidermal cyst. However, histopathologic examination revealed a stratified squamous epithelium without a granular layer, which corresponded to trichilemmal keratinization. The contents of the cyst consisted ofa homogenous eosinophilic material. The cyst was diagnosed as a trichilemmal cyst.