外毛根鞘癌―各種皮膚腫瘍との関連とその独立性―

抄録

1) The histopathological findings of trichilemmal keratinization (TK) and the presence of clear cells are not always diagnostic for “trichilemmal carcinoma”, they are non-specific findings that may be observed in various skin tumors, such as Bowen's disease, Bowen carcinoma, solar keratosis and squamous cell carcinoma.
2) Solar keratosis (bowenoid type) occasionally show the features of “trichilemmal carcinoma”, supporting the concept that at least some percentage of “trichilemmal carcinoma” is just an advanced form of a solar keratosis.
3) Trichilemmal carcinoma, Bowen's disease, Bowen carcinoma and malignant proliferating trichilemmal tumor (MPTT) are related and overlapping tumor concepts, so it is necessary to establish criteria to differentiate among them, if they are indeed different.
4) The diagnosis of MPTT should only be made when malignant transformation is observed in a proliferating trichilemmal cyst (tumor), and should not be used as a synonym for a “trichilemmal carcinoma” or a Bowen carcinoma which occasionally shows cyst-like structures.
5) To establish “trichilemmal carcinoma” as a tumor entity, it is necessary to define what is trichilemmal differentiation histopathologically.