Abstract
A flat elevated lesion with a central depression was observed in the lower gastric body of a 75-year-old man. The epithelium of the first biopsy specimen was atypical, and no significant change was apparent 3 weeks later. The epithelial surface was covered with a whitish substance rendering it difficult to observe the surface structure. Three months later, the lesion had grown. A biopsy revealed malignancy, and endoscopic submucosal dissection was performed. A mucinous carcinoma exhibiting submucosal invasion was histopathologically identified. Additional surgery was performed, but lymph node metastasis developed. Thus, an early-stage mucinous carcinoma may rapidly grow and metastasize. If a flat elevated lesion covered with a whitish substance (indicative of an early-stage mucinous carcinoma) is observed, diagnostic endoscopic submucosal dissection or strict follow-up is required.
