Diagnosis: Pilomatricoma/Pilomatrixoma, histopathology
Solitary, firm to rock-hard, subcutaneous nodule. Most common on face, neck, upper extremities in children. Slow-growing, often skin-colored or bluish.
Surgical excision (curative). Recurrence is rare after complete excision.
• Epidermal inclusion cyst • Dermoid cyst • Pilomatrical carcinoma • Calcified lymph node • Foreign body granuloma • Basal cell carcinoma
• Also known as calcifying epithelioma of Malherbe • Most common in children and young adults — solitary, firm, deep-seated nodule • "Tent sign": stretching overlying skin reveals multifaceted surface • Histology: basophilic cells (viable) transitioning to shadow/ghost cells (anucleate) — pathognomonic • Calcification and ossification common • Beta-catenin (CTNNB1) mutation — same pathway as Gardner syndrome • Multiple pilomatricomas: consider Gardner syndrome (APC mutation) or myotonic dystrophy • Pilomatrical carcinoma is the rare malignant counterpart
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