LAUSR

Rationale: Desmoid fibromatosis is a rare benign tumor, but due to its rarity and diverse clinical course, treatment guidelines have not been established. However, since a good prognosis can be expected, an accurate diagnosis and appropriate treatment are required. We describe a rare case of desmoid fibromatosis on young female that presented as huge abdominal mass. Patients concerns: A 28-year-old female with left upper abdominal pain 1 month ago was referred. Diagnoses: Abdominal computed tomography and magnetic resonance imaging revealed a heterogeneous soft tissue mass approximately 29 × 17 cm in size in the left abdomen with abdominal wall invasion and pathological fracture in costochondral junction of the left 8th to 10th ribs. Interventions: Surgical resection was performed. Outcomes: 33 × 23 × 6 cm sized tumorous mass showed proliferation of bland fibromatosis and myofibroblast with nuclear β-catenin expression on pathological examination. Desmoid fibromatosis arising from intra-abdominal soft tissue with ribs and pericardium invasion was diagnosed. Lessons: The mainstay of treatment of symptomatic desmoid fibromatosis is surgical resection, and in the case of abdominal tumor, it can be more dangerous when it invades adjacent organ. We report a case that required additionally multidisciplinary approach for surgery and postoperative treatment of huge abdominal desmoid tumor which infiltrate bone and pericardium beyond abdominal cavity.