皮膚上皮性腫瘍/囊腫におけるトピックス

抄録

Four topics about cutaneous epithelial cysts and tumors are summarized in this article. The first topic is infundibular cysts with characteristic papillary projections, which we first reported in 2006 as trichoblastic infundibular cysts. In our recent article, we described that the observed characteristic projections do not differentiate towards follicular germinative cells; therefore, we propose to rename this lesion. The second is tubulopapillary cystic adenoma with apocrine differentiation as a unifying concept for syringocystadenoma papilliferum, tubular adenoma, and apocrine gland cysts, which we first proposed in 2016. We demonstrated that these three tumors are composed of the same components with differing architecture by summarizing clinicopathological data from over 300 cases. The clinicopathological findings of this entity are summarized in this article. The third is a new classification of cutaneous sebaceous neoplasms, including sebaceous borderline neoplasms (low-grade sebaceous carcinoma). The former classification of sebaceous neoplasms included sebaceous adenoma, sebaceoma, sebaceous epithelioma, and ocular and extraocular sebaceous carcinoma. The newly proposed classification of sebaceous tumors has 3 categories: sebaceoma (a benign neoplasm with well-defined architecture and no atypia of neoplastic cells), sebaceous borderline neoplasm (low-grade sebaceous carcinoma; a tumor of intermediate malignancy with well-defined architecture and nuclear atypia), and sebaceous carcinoma (a malignant tumor that exhibits invasive growth and notable nuclear atypia). The last is in situ lesions of sebaceous carcinoma. Of note, there are two types of in situ extraocular sebaceous carcinoma: one is a malignant tumor with sebaceous differentiation that is limited to the epidermis and/or adnexal epithelium, whereas the other originates from squamous cell carcinoma in situ, including actinic keratosis and Bowen's disease, as we previously reported.