明らかな皮膚病巣がなく脊椎・骨盤転移を認めた悪性黒色腫の1例

Metastasis to the Spine and Bony Pelvis Bone by Malignant Melanoma of Unknown Origin. Case Report

　患者は32歳の男性で，腰痛および左股関節痛，腹部のしびれが出現した．MRIで第11胸椎に腫瘍を認め，骨シンチグラムで骨盤にも集積を認めた．胸部腹部骨盤CTおよび上部・下部消化管内視鏡検査で明らかな原発巣はなかった．骨盤からの骨生検で悪性黒色腫の診断を受けたが明らかな皮膚・粘膜病変はなかった．化学療法のため皮膚科入院中に対麻痺・膀胱障害が生じたので，脊椎後方除圧固定術を施行した．麻痺は残存したが，除痛が得られた．診断には骨生検が有用であり，原発巣不明の転移性脊椎腫瘍の原因として悪性黒色腫も検討すべきと考えられた．

　We report the case of a 32-year-old man who presented with a long-term history of back pain, left coxalgia, and abdominal numbness. MRI revealed tumor lesions at level of the eleventh thoracic vertebra, and bone scintigraphy showed tumor lesions in the left pelvis. Examination of a biopsy specimen of the pelvic lesion suggested metastasis by a malignant melanoma, but clinical investigations failed to identify a primary lesion in the skin or mucous membranes. Chemotherapy was administered, but paraplegia and a bladder disturbance developed one month later. Partial laminectomy and posterior spinal fusion were performed, and the histopathological diagnosis of the surgical specimen was also melanoma metastasis. Chemotherapy was continued postoperatively, and the patient was satisfied with the pain relief, but the paraplegia persisted. The bone biopsy was useful in making the diagnosis of a metastatic tumor by a malignant melanoma of unknown origin.