[Trichilemmal horn: a new case and review of the literature].

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.