Giant pilomatrixoma: a distinctive clinical variant: a new case and review of the literature.

Pilomatrixoma is a benign adnexal tumor very common in pediatric age and in young adults that derives from follicular matrix cells. Although clinically it usually presents as a subcutaneous nodule of bluish color less than 3cm in size, multiple clinicopathological variants have been described in the literature. Among these we can find the giant pilomatrixoma, a rare clinical variant that reaches a size greater than or equal to 4cm and can simulate the clinical presentation of a malignant neoplasm. We report a 59-year-old man with an exophytic and ulcerated nodule in the left parotid region that was removed with the suspected diagnosis of a cutaneous squamous cell carcinoma. Histopathological analysis showed a proliferation of basaloid cells with areas of transition to ghost cells, under granulation tissue, hemorrhage, and an ulcerated epidermis. Thus, the diagnosis of giant pilomatrixoma was made. We reviewed the literature and found a total of 53 articles that report a total of 71 cases of giant pilomatrixoma. It is important to recognize this clinical subtype of pilomatrixoma because, apart from the possibility of being clinically confused with malignant lesions, the clinicopathological differential diagnosis must be made with the proliferating pilomatrixoma and pilomatrixcarcinoma.