耳介に発生したDesmoplastic Spitz 母斑の1例

A Case of Desmoplastic Spitz Nevus Arising on an Auricle

はじめに

　Spitz母斑は色素性母斑の一種であるが，その母斑細胞は大型で多形性をもつことから悪性黒色腫との鑑別が問題となる。今回われわれは，5歳，女児の右耳輪に発生したSpitz母斑の亜型の1つであるdesmoplastic Spitz nevus（以下，DSN）を治療する機会を得た。耳介での発生例はまれであり，若干の文献的考察を加え報告する。

　It can be difficult to distinguish Spitz nevus from malignant melanoma. We describe the case of a 5-year-old girl with a desmoplastic spitz nevus（DSN）that developed on an auricle. One year prior to her visit to our hospital, a skin-colored to erythematous nodule appeared on her right auricle. The nodule gradually increased in size and was eventually accompanied by erosions and scaling on its surface. A skin biopsy was performed, and a diagnosis of Spitz nevus was made; however, the possibility of amelanotic melanoma could not be ruled out. Under general anesthesia, the nodules of the helix and the scaphoid fossa were excised and reconstructed with a flap from the back surface of the auricle and a skin graft. The pathological and immunopathological examinations showed a definite diagnosis of DSN.

　One year and nine months after the surgery, there was no recurrence, and the shape of the helix was relatively well preserved.

　DSN is a relatively rare subtype of spitz nevus that usually arises on an extremity of young adults. Histologically, DSN is characterized by collagen hyperplasia of the dermis and an interfollicular filamentous proliferation of nevus cells. Junctional activity, follicular formation, and mature melanocytes are usually absent.

　Careful diagnosis is required to distinguish DSN from malignant melanoma, especially desmoplastic malignant melanoma（DMM）.