Duodenum-derived fibromatosis that invaded the muscular layer of intestinal wall

RATIONALE Intraabdominal fibromatosis is a rare benign tumor that often affects the mesentery or retroperitoneum, and can infiltrate adjacent organs. However, it is rare for fibromatosis to arise from the small intestinal wall. PATIENT CONCERNS A 27-year-old female with a tangible abdominal tumor is described. DIAGNOSES The computed tomography (CT) scan revealed a 7.5 cm, small intestine-associated tumor in the right abdomen. INTERVENTIONS The patient received tumor resection and intestinal anastomosis. OUTCOMES Further pathological examination confirmed the tumor as a duodenal fibromatosis that infiltrated the intestinal wall. To the best of our knowledge, this is the first report of a duodenum-derived fibromatosis that invaded the muscular layer of the intestine. LESSONS Our study demonstrated that an unexplained abdominal mass should be noteworthy and properly treated.