Pilomatricoma, a benign tumor arising from hair follicle matrix cells, commonly appears as a slow-growing, firm, nontender nodule on the head and neck region. This report describes an atypical variant of pilomatricoma in a 12-year old Filipino female who presented with a 4-week history of a solitary rapidly-enlarging nodule morphologically resembling a proliferating keratoacanthoma on the right arm. Histopathologic diagnosis of pilomatricoma with suppurative and granulomatous inflammation was made and wide local surgical excision was done. This article highlights the importance of including pilomatricoma in the differential diagnosis of pediatric patients presenting with a firm, solitary, rapidly-growing nodule on sites other than the head and neck region.