Primary small intestine angiofibroma of soft tissue (AFST) with intussusception: an extremely rare case report and review of literature.

BACKGROUND: Angiofibroma of soft tissue (AFST) is a rare benign mesenchymal tumor, typically occurring in the deep soft tissues of the extremities. Histologically, it is characterized by bland spindle cells and an abundant branching vasculature. Owing to the absence of specific markers, this lesion is frequently misdiagnosed as other spindle cell neoplasms, leading to inappropriate clinical management. Primary AFST arising in the small intestine has not been formally reported to date. This report presents a case of primary small intestinal AFST manifesting initially as intussusception and intestinal obstruction. CASE PRESENTATION: A 43-year-old male patient underwent emergency surgery for acute intestinal obstruction complicated by intussusception. A mass was found within the lumen of the terminal ileum, and segmental small intestine resection was performed. Pathological examination revealed a polypoid mass measuring 6.0 × 3.0 × 3.0 cm. Microscopically, the tumor consisted of morphologically uniform spindle cells and numerous thin-walled, branching blood vessels, exhibiting locally infiltrative growth. Immunohistochemical staining revealed that the tumor cells were diffusely positive for CD68 and CD163, and negative for CD31, CD34, CD117, DOG-1, S-100, β-catenin, ALK, CD21, cytokeratin (CK), Desmin, Sox-10, Calretinin, Myoglobin, CD1a, HMB45, Melan-A and STAT6. Based on these findings, a diagnosis of primary small intestinal angiofibroma of soft tissue (AFST) was made. Although histologically benign, AFST can induce acute abdominal complications such as intussusception when it reaches a substantial size, necessitating clinical awareness. Definitive diagnosis relies on characteristic histomorphology, a supportive immunophenotype (CD68/CD163 positivity), and molecular genetic studies. Complete surgical excision constitutes the mainstay of treatment and is associated with a favorable prognosis.