外毛根鞘癌 臨床と病理組織

Abstract

Malignant trichilemmoma (MT) is cutaneous adnexal neoplasm of external hair sheath origin, whose histologic feature is often confused with those of malignant proliferating trichilemmal tumor (MPTT) . In order to investigate the possibility that MT might differ from MPTT clinically and histologically, we studied 37 cases of MT and 30 MPTT. MT regarded as the malignant counterpart of trichilemmoma, manifests as solitary keratotic or ulcerated nodules. MT is often misdiagnosed as Bowen disease. Microscopically MT consists of multiple intradermal epithelial lobules in continuity with the epidermis. The tumor is composed of large glycogenrich clear cells with peripheral palisading that exhibit areas of trichilemmal keratinization. Ultrastructurally intracytoplasmic focal dyskeratosis was observed. Despite the frequent presence of histologically malignant features, it has a relatively benign clinical behaviour. MPTT showed clinically ulcerated, teleangiectatic or keratotic nodules. Histologically, MPTT had the presence of cystic configuration that extended from epidermis into reticular dermis. They were more prone to local recurrence and metastasis. We conclude that histologic, ultrastructural, and immunohistochemical studies should be performed to offer a more complete definition and classification of these neoplasms.