■綜説
Pigmented epithelioid melanocytoma（PEM）とは？―WHO分類に記載された新概念
伊東 慶悟
日本医科大学武蔵小杉病院皮膚科
What Is Pigmented Epithelioid Melanocytoma (PEM)? It Is Published by New WHO Classification of Skin Tumors, 2018
Keigo Ito
Department of Dermatology, Nippon Medical School Musashi Kosugi Hospital
Pigmented epithelioid melanocytoma (PEM) is a new melanocytic neoplasm composed of heavily pigmented epithelioid and dendritic cells, with metastatic potential limited to regional lymph nodes. It was previously diagnosed as human animal-type melanoma and epithelioid blue nevus. Current experience indicates that it is best considered as a borderline melanocytic neoplasm or a low-grade melanoma. PEM has unique demographic, clinical and histological features. It can occur as a sporadic lesion or in patients with Carney complex. It is a rare tumor with a predilection for young people, including children. All racial groups are affected. It has a generalized distribution, including localization to the extremities, head and neck, and trunk. These lesions occur as a slow-growing pigmented nodule or papule. Histopathologically, it is composed of varying proportions of pigmented dendritic and epithelioid melanocytes admixed with melanophages. The diagnostic epithelioid cells are round, polygonal, or elongated, and they range in size from medium to large. A subset of PEMs show loss of expression of the protein product of PRKAR1A, which is a mutation of families with Carney complex. PEM is an indolent melanocytic tumor with metastatic potential limited to regional lymph nodes and otherwise rare distant metastasis. No deaths from the disease have been reported.
日医大医会誌 2020; 16(1), 18-24
Key words
pigmented epithelioid melanocytoma (PEM), melanocytoma
Correspondence to
Keigo Ito, Department of Dermatology, Nippon Medical School Musashi Kosugi Hospital, 1-396 Kosugi-cho, Nakahara-ku, Kawasaki Kanagawa 211-8533, Japan
E-mail：keigo-ito@nms.ac.jp
受付：2019年11月26日 受理：2020年1月23日 |
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