Plexiform fibromyxoma: a clinicopathological and immunohistochemical analysis of two cases with a literature review

OBJECTIVE: This article aimed to study the clinicopathological features, immunophenotypes, and differential diagnoses of plexiform fibromyxoma (PF). METHODS: We searched clinical and pathology databases of our hospital for patients with histologically confirmed PF from 2007 to 2020 and reviewed the relevant English and Chinese language literature. RESULTS: Two cases of PF were identified, a 67-year-old woman and a 23-year-old man. Both patients presented with melena and anemia and underwent partial gastrectomy. Histologically, the tumors exhibited a plexiform growth pattern in the gastric submucosa and the presence of bland-looking spindle cells in the fibromyxoid stroma with the formation of small blood vessels. Immunohistochemically, the two cases were strongly positive for vimentin, smooth muscle actin, and muscle-specific actin and negative for CD117, discovered on gastrointestinal stromal tumors protein 1, CD34, CD10, S100, desmin, H-caldesmon, estrogen receptor, progesterone receptor, β-catenin, and cytokeratin. CONCLUSIONS: PF is a rare mesenchymal tumor of the stomach that can be distinguished from other gastrointestinal mesenchymal tumors based on its distinctive morphology and immunophenotype.