直腸黒色腫の1例

A Case of Rectal Melanoma

要旨●背景にMALTリンパ腫を有する直腸黒色腫を経験した．患者は70歳代，女性．MALTリンパ腫に対して化学療法後経過観察中の大腸内視鏡検査において下部直腸（Rb）に2個の隆起性病変が認められ，ともに黒色調ではなかったが，拡大内視鏡所見では直腸黒色腫を示唆する所見が認められた．2病変それぞれに内視鏡切除が行われ，病理組織学的にはいずれも黒色腫の診断で，1病変はMALTリンパ腫と併存していた．乏色素性直腸黒色腫のまれな1例であり，本症例における内視鏡診断上注目すべき点と病理組織学的特徴を共有することで，今後の診断・治療方針の一助となることが期待される．

　We encountered a case of rectal melanoma arising in the background of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue（MALT lymphoma）. A woman in her 70s who was undergoing surveillance colonoscopy after chemotherapy for MALT lymphoma was found to have two elevated lesions in the lower rectum. Both lesions exhibited characteristic features of rectal melanoma with poor pigmentation. We performed endoscopic resection of each lesion, and histopathological examination confirmed melanoma in both ; one lesion also demonstrated coexistence with MALT lymphoma. This represents a rare case of oligomelanotic rectal melanoma. By sharing the notable endoscopic findings and histopathological characteristics observed in this case, we aim to contribute to future diagnostic and therapeutic decision-making.