Pediatric Pilomatrixomas: Four Atypical Clinical Presentations

Pilomatrixoma, also called Malherbe's calcifying epithelioma or pilomatrixoma, is a benign adnexal tumor that originates from keratinocytes (cells of the hair matrix, the internal sheath of the hair root or the cortex) and constitutes the second most prevalent skin neoplasm in children. These lesions are typically slow-growing, firm, nodules located on the head, neck, trunk, and extremities (in decreasing order of frequency). Due to the rarity, combined with their varied clinical presentations, pilomatrixomas are often misdiagnosed. Current pilomatrixoma classification schemes remain controversial. In this article, we present 4 pediatric patients that exemplify different clinical and atypical scenarios of the same tumor. Accordingly, we invite future studies to create a novel system for the classification of pilomatrixomas based on atypical clinical characteristics, including lesion morphology, number, size, and anatomic location.