[Clinicopathological features of very well-differentiated adenocarcinoma of the stomach].

To investigate the clinicopathological features of very well-differentiated adenocarcinoma (VWDA) of the stomach. The clinicopathological data of 12 cases of VWDA of the stomach were collected retrospectively at the People's Liberation Army Joint Logistics Support Force 989 Hospital (formerly 152 Hospital), Pingdingshan, China, from January 2013 to May 2021. The histological characteristics and immunophenotypes were observed and analyzed with review of current literature. There were 8 males and 4 females with a median age of 63 years (range 47 to 80 years). The tumor involved in the upper part of the stomach in 6 cases, the middle part in 2 cases, and the lower part in 4 cases. The median diameter of the tumors was 17 mm (range 5-65 mm). The tumor cells were similar to absorbent cells, Paneth cells, foveolar epithelial cells, and goblet cells. The cells were arranged in a single layer, and the nuclei were slightly enlarged and located at the base. The nuclei were fusiform to slightly irregular, with loss of nuclear polarity. Early tubular VWDA was found in 9 cases, and the tumor glands were similar to intestinal metaplasia. In two cases the tumors infiltrated into the submucosa. The lesions in the mucosa and submucosa showed the glands with cystic expansion, bending, branching, spiky and abortive growth pattern. One case of early papillary tubular VWDA was confined to the mucosal layer and composed of foveolar-type epithelial cells. There were two cases of advanced papillary tubular VWDA, which consisted of foveolar-type epithelial, pyloric glands, or mucinous neck cells and were associated with intra-lymphatic cancer embolus and lymph node metastases. Background mucosal atrophy and intestinal metaplasia were observed in all cases. Immunohistochemical staining showed intestinal type VWDA in 1 case, mixed gastrointestinal type VWDA in 9 cases, and gastric type VWDA in 2 cases. The Ki-67 proliferation index of 8 cases limited to the mucosa was 40%-70%, 2 cases of infiltration into the submucosa and 2 cases of advanced carcinoma was 10%-25%. All the tumors showed a wild type of p53 protein expression pattern and negative HER2. Adenocarcinoma or high-grade dysplasia was diagnosed on preoperative biopsy in 5 cases, and chronic atrophic gastritis with intestinal metaplasia in 7 cases. The median follow-up time was 28 months (range 12-72 months). No recurrence was found in the 10 patients with early cancer. Of the two patients with advanced carcinoma, one patient had lung metastases and the other died. Gastric VWDA is a rare low-grade malignancy with structural features of highly differentiated adenocarcinoma and extremely low cytological atypia. The diagnostic value of structural abnormality is significantly greater than cytological atypia. The invasive growth of irregular glands in the deep mucosa and submucosa is reliable evidence for diagnosis. The diagnosis of intramucosal VWDA is challenging and very difficult in some biopsy specimens.