Pilomatrixoma. Light micrograph (LM) of a section of a Pilomatrixoma (also known as pilomatricoma and calcifying epithelioma of Malherbe). This is a benign tumor of the hair matrix. It mainly affects children and young adults with a female predominance. The majority of patients are under 10 years of age. It usually presents as a solitary, painless, slow-growing, firm to hard nodule on head, face, upper extremities, and neck. At low magnification, pilomatrixoma has a biphasic appearance consisting of solid blue areas of basaloid cells and eosinophilic areas of ghost cells. There is usually a sharp demarcation between the two components due to abrupt keratinization of basaloid cells into ghost and shadow cells. Magnification: x50 when printed at 10 centimetres wide. Human tissue.