腹壁原発悪性顆粒細胞腫の1例

Malignant Granular Cell Tumor of the Abdominal Wall. Case Report

　症例は61歳の女性で，数年前から左側腹部腫瘤を自覚していた．初診時のCT(computed tomography)で左腹壁腫瘤に加え，肝，肺，右殿部脂肪層内に腫瘤を認めた．腹壁およびその後，殿部の生検で好酸性顆粒状胞体を有する大型の腫瘍細胞が増生していた．核異型は軽度であった．腫瘍細胞はS-100蛋白とCD68が陽性で，MIB-1(mindbomb homolog 1)陽性率が高く，腹壁原発悪性顆粒細胞腫であり，右殿部への転移と診断した．顆粒細胞腫は本例のように異型が軽度でも悪性の転帰をとることがある．顆粒細胞腫においてもMIB-1陽性率が高い場合は，良悪性の判断に有用であった．

　A 61-year-old woman was aware of having a left-sided abdominal tumor for several years.　A computed tomography scan revealed a tumor in her left abdominal wall and lesions in the both lungs, liver, and subcutaneous fat layer of the right buttock.　Examination of incisional biopsy specimens of the abdominal wall and buttock revealed large tumor cells containing abundant granular eosinophilic cytoplasm growing within the striated muscle.　The cells were positive for S100 protein and CD68.　Although the nuclear atypia was mild, since the MIB-1 index was high, and distant metastatic lesions were already present, we made a diagnosis of malignant granular cell tumor of the abdominal wall.　It is difficult to determine whether granular cell tumors are benign or malignant on the basis of the morphological findings alone.　As in this case, the disease may be advanced even when the nuclear atypia is mild.　The MIB-1 index is useful for determining whether a granular cell tumor is benign or malignant.