Navigating Diagnostic Uncertainty: A Case of Pediatric Arm Swelling Unravelled as Pilomatrixoma

Abstract

Pilomatrixoma is a benign superficial appendageal tumour arising from hair follicle matrix, usually confirmed via histopathology, but its cytologic features vary with disease stage, mimicking other lesions. We present a case of a seven-year-old girl who underwent fine needle aspiration of a left arm nodule. Smears revealed clusters of ovoid cells, multinucleated giant cells and calcified keratinous material. Cytology suggested pilomatrixoma or calcified epidermal cyst, with histopathology confirming pilomatrixoma. This case reiterates variability in cytologic features of pilomatrixoma and also creates awareness about its mimics as an accurate preoperative aspiration report guides decision making and surgical management.