Three cases of giant pilomatrixoma – considerations for diagnosis and treatment of giant skin tumours with abundant inner calcification present on the upper body

Abstract

Pilomatrixoma frequently occurs as a solitary, small tumour on the face or upper extremities of people younger than 20 years. We report three cases of giant pilomatrixoma. In all these cases, outward appearances and imaging investigations suggested malignant tumours. Preoperative biopsies suggested that case 1 was a basal cell carcinoma, but cases 2 and 3 had no malignant features on biopsy. Two of the cases experienced rare complications - hypercalcaemia caused by parathyroid-related protein (PTHrP) production and multiple occurrences. All three tumours were removed with a 1-3-cm margin. The postoperative histopathologies showed pilomatrixoma in all three cases. Rarely, pilomatrixoma develops to a giant size with various atypical outward appearances consistent with a malignant tumour. Preoperative clinical appearances frequently lead to misdiagnosis, and preoperative examinations are unreliable. Therefore, when a giant tumour with abundant inner calcification is present in a young patient, the possibility of a pilomatrixoma should be considered.