oncocytic differentiationを示した胃カルチノイドの1例

Oncocytic Carcinoid of the Stomach, Report of a Case

要旨　患者は54歳，男性．胃カルチノイドの疑いで手術施行．肉眼的に胃角部前壁側に15×12×4mmの粘膜下腫瘍を思わせる隆起性病変があり，中央に小さな白苔を有していた．腫瘍は病理組織学的に前腸由来の好銀性カルチノイドに一致する所見であったが，3つの異なる組織像，すなわち①ロゼット様構造を示す部分，②髄様腺管癌様の構造を示す部分，③oncocyteの集団，から構成されていた．特に③の部分は通常のカルチノイドには認め難い組織像であったが，免疫組織化学的検索によってガストリン，S-100蛋白，NSEが証明された．更に電子顕微鏡によっても内分泌顆粒と多数のミトコンドリアが細胞質内に認められた．肺のカルチノイドにはoncocyteが出現するという報告はあるが，今回の症例のように胃のカルチノイドにもoncocyteが出現することが証明され，カルチノイド腫瘍の組織多様性を改めて確認した．

　A 54-year-old man was admitted to our hospital with the diagnosis of carcinoid tumor of the stomach. An operation was performed on Nov. 22nd, 1987. The tumor was situated at the anterior wall of the angular region of the stomach. It measured 15 × 12 × 4 mm. Histopathological study showed that it was constituted of three histological components as follows; rosette-like structure, medullary-carcinoma-like structure, oncocytic cell proliferated area. All three components were intermixed and had mutually effected one another. Oncocytic cells were stained positive with Grimelius stain but negative with Fontana-Masson stain. Immunohistochemical study showed positive S-100 protein and NSE in the cytoplasm of the oncocytic cells. Small endocrine granules and abundant mitochondrias were also detected in the cytoplasm of the oncocytic cells by electron microscopic study. Although there are a few reports of oncocytoma including oncocytic carcinoid of the lung, only one case of oncocytoma of the stomach has been reported. Our case illustrated the fact that oncocytoma or oncocytic carcinoid can occur not only in the lung but also in the stomach. This carcinoid tumor showed variable pathological features and represents one of the neuroendocrine carcinomas.