Trichilemmal Horn: a New Case and Review of the Literature

Abstract Trichilemmal horn, or trichilemmal keratosis, is an uncommon benign neoplasm of follicular lineage with trichilemmal differentiation. The essential characteristics of this tumor are its clinical presentation in the form of a cutaneous horn with trichilemmal keratinization apparent in the histology study (with a hyperplastic epithelium giving rise to dense, orthokeratotic eosinophilic keratin). We present a new case of this type of tumor in an 82-year-old woman who developed a solitary lesion on her scalp after surgical removal of a trichilemmal cyst. On the basis of the pathology report, the tumor was diagnosed as trichilemmal horn. We review the 33 reports of this tumor in the literature to date.