Pilomatrix carcinoma - A clinicopathologic study of six cases and review of the literature

Pilomatrix carcinoma, the malignant variant of pilomatrixoma, is a rare ent ity. The authors report on six patients with pilomatrix carcinoma and revie w the pertinent literature. The lesions showed a predilection for elderly i ndividuals (mean age, 61 years) with a male:female ratio of 5:1, and they p resented as dermal or subcutaneous tumors located on the head and neck ( 5 neoplasms) and chest (1 neoplasm). Tumors varied in size from 0.6 cm to 2.5 cm. (mean, 1.78 cm). None of the lesions recurred after wide local excisio n. On scanning magnification, all tumors showed the architectural features of a malignant neoplasm (asymmetry and poor circumscription, presence of se veral markedly sized and variably shaped basaloid aggregations, and ulcerat ion). The tumors were composed of pleomorphic basaloid cells with prominent nucleoli and frequent atypical mitoses accompanied by central areas with k eratotic material, shadow cells, and foci of necrosis. The tumor nests were surrounded by a desmoplastic stroma and infiltrated the adjacent tissues. Vascular or perineural infiltration was not observed. In one case, the basa loid cells contained abundant melanin pigment in their cytoplasms. Pilomatr ix carcinoma is a neoplasm of low-grade malignancy that should be distingui shed from the conventional pilomatrixoma and its variants (aggressive pilom atrixoma and proliferating pilomatrixoma), matricoma, and basal cell carcin oma with matrical differentiation. Clinicians and pathologists should be aw are of the occurrence of pilomatrix carcinoma because of its potential for distant metastases.