A case of pulmonary adenocarcinoma with sarcomatous elements initially manifested as a submucosal tumor of the stomach.

A case of pulmonary adenocarcinoma, which was initially manifested as a gastric submucosal tumor, is presented. Endoscopy showed a submucosal tumor in the fundic region in a 79-year-old Japanese woman. Initial biopsy specimens of the stomach revealed atypical spindle cell proliferation, suggesting primary leiomyosarcoma of the stomach. However, biopsy specimens obtained one year later were diagnosed as malignant lymphoma or malignant histiocytosis of the stomach. Autopsy revealed a large necrotic lesion in the right S8 region with metastases in multiple organs. Microscopy demonstrated well to moderately differentiated adenocarcinoma containing spindle or pleomorphic sarcomatous elements. Metastatic nodules including the gastric tumors all showed sarcomatous elements with no epithelial component. Immunohistochemistry showed positive reactions for keratin, epithelial membrane antigen, and carcinoembryonic antigen in areas of carcinoma, whereas most of the sarcomatous elements revealed no positivity for any of the antibodies used, except for focal keratin and EMA positivity in the primary site. This is a rare case of pulmonary adenocarcinoma with sarcomatous elements discovered as a gastric tumor at initial diagnosis, resulting from metastasis of the sarcomatous element in the submucosa.