Pilomatricoma lesion on the back of an 8 year old Hispanic male patient. This benign (non-cancerous) growth is caused by a mutation in hair matrix cells in the hair follicle. White areas are due to calcification, which makes the lesion hard. Lesions are most often found on the head or neck, but may occur anywhere. Pilomatricoma is more common in children and females. Treatment is with surgical excision.