典型的な粘膜下腫瘍様形態を呈した早期胃膠様腺癌の1例

Early Gastric Mucinous Adenocarcinoma Showing Typical Features of a Submucosal Tumor, Report of a Case

要旨　71歳女性の胃体中部前壁に発生した粘膜下腫瘍様形態を呈する早期胃膠様腺癌の1例を報告する．本症例は肉眼的には典型的な粘膜下腫瘍の形態を呈しており，隆起表面は周囲と同じ萎縮粘膜で覆われていたが，頂部に認めた臍窩からの生検で癌細胞を認めた．そこで，性状診断および治療適応の決定を目的として行った超音波内視鏡検査で，腫瘍が第3層内に限局していることが確認されたため，診断および治療を目的として，内視鏡的切除術を行い，粘膜下に限局性に発育した膠様腺癌と診断された．

　The patient: a woman aged 71. Endoscopic examination of the stomach for screening showed a smooth, sharply circumscribed elevated lesion accompanied with depression on the anterior wall of the middle corpus. It was suggestive of a typical submucosal tumor, but as biopsy revealed malignant cells of signet-ring type, we took also into account (the possibility that it was a type of) metastatic carcinoma, with this in mind we performed EUS examination for the diagnosis of the nature of the tumor. We could diagnose that the tumor mainly existed in the submucosal layer, and that it was separate from the 4th layer. Then we took out the tumor endoscopically for the purpose of clarifying the whole shape, and determining what therapy to use. Because the patient was suffering from some complication.

　The resected specimen showed an elevated lesion, measuring 17×12 mm, with a depression in the center, measuring 4×3 mm. Histologically, the chief part of the elevation was tumor tissue in the submucosa showing nodular proliferation, and forcing up the normal mucosa from underneath. Cancer cells of signet-ring cell type were seen floating in the mucous lake in the submucosa. The diagnosis was “poorly differentiated mucinous adenocarcinoma with depth of invasion reaching the submucosa.”

　Mucinous adenocarcinoma is least frequent among adenocarcinomas of the stomach, and its histological type is confirmed only when it proliferates beneath the submucosa at an early stage of proliferation.

　Early gastric mucinous adenocarcinoma, as in the present case, localized within the submucosa is of rare occurrence. We can find only 8 cases of mucinous adenocarcinomas among the 30 cases since 1981, which have been reported as showing features of a submucosal tumor. Among these, early gastric mucinous adenocarcinomas including our own case, number only 3 cases.

　EUS examination is very useful for clarifying the whole shape of a tumor and deciding a plan for therapy.