転移性腫瘍の形態を示した形質細胞腫胃浸潤の1例

Diffuse Gastric Plasmacytoma Involvement Mimicking a Metastatic Gastric Tumor, Report of a Case

要旨●患者は70歳代，男性．巨大な副鼻腔腫瘤の生検にて高悪性度の形質細胞腫・IgGκ型と診断された．PET-CTで副鼻腔腫瘤の他に胸骨柄に限局性の集積像が認められた．骨髄には病変を認めなかったため，多発性形質細胞腫と診断し，化学療法・放射線治療を開始した．化学療法施行から3か月後の治療効果判定のために施行したPET-CTにて，多発する胃内集積像を認めた．精査のため上部消化管内視鏡検査を施行したところ，胃内に径10mm前後の中心に陥凹・びらんを伴った上皮下腫瘍様・0-IIa＋IIc型様の発赤調隆起病変が多発していた．生検による病理組織学的所見では，副鼻腔腫瘤の所見と同様の形質細胞腫・IgGκ型の診断．以上により，転移性腫瘍の形態を呈し，胃内に多発した，極めてまれな形質細胞腫の胃浸潤病変と診断した．

　A man in his 70s, with a biopsy diagnosis of extramedullary plasmacytoma（immunoglobulin Gκ type）in the nasal sinus, underwent PET-CT（positron emission tomography-computed tomography）, which revealed a giant plasmacytoma in the sinus and a localized accumulation on the sternal stalk. No lesion was found in the bone marrow, and the patient was diagnosed with multiple plasmacytoma. Three months following chemotherapy, another PET-CT, performed to observe the extent of the therapeutic effect, revealed multiple gastric lesions. Further evaluation using esophagogastroduodenoscopy displayed multiple reddish, elevated subepithelial or 0-IIa＋IIc tumor-like lesions approximately 10mm in diameter, with depressions and erosions in the center. These lesions occurred primarily in the greater curvature of the gastric body and fornix. The histologic examination of the gastric lesion biopsies indicated a similarity of the lesions with the sinus plasmacytoma. Hence, the patient was diagnosed with diffuse gastric plasmacytoma involvement that mimicked a metastatic gastric tumor.