Rare invasive inflammatory fibroid polyp presenting as small bowel intussusception: Two case reports and review of the literature.

RATIONALE: Inflammatory fibroid polyp (IFP) is a rare benign neoplasm of uncertain etiology and mostly occurs in the stomach, emerging from the submucosal layers. Intussusception causing bowel obstruction due to IFP is even rare. We present 2 cases of IFP in adults, which caused small bowel intussusception and broke through the submucosa uncommonly.

PATIENT CONCERNS: This article reports 2 patients presenting with abdominal pain. One patient was an 81-year-old Chinese man, who presented with a 7-day history of intermittent left abdominal pain. The other patient was a 49-year-old Chinese woman with a 5-day history of intermittent lower abdominal distension pain. Their abdominal computed tomography both demonstrated small bowel intussusception.

DIAGNOSES: The 2 patients were diagnosed with small bowel intussusception.

INTERVENTIONS: Both patients underwent surgical resection of a segment of the small intestine. During the old man's operation, a 2.5 cm × 3.5 cm polypoid tumor was found in the jejunum, at a distance of 60 cm from the ligament of Treitz. During the women's operation, a 3.6 × 3.7 cm polypoid lesion was found in the ileum, which protruded into, and completely occluded the lumen.

OUTCOMES: The 2 patients had an uneventful recovery, being discharged about 1 week postoperatively without any postoperative complications. Morphologically, the old man's intraluminal intestinal mass had invaded muscularis propria, and was negative for CD34 immunohistochemically, creating difficulties in diagnosing IFP. The woman's intraluminal intestinal mass had infiltrated into the serosal layer. Ultimately, the pathological diagnosis for both patients was IFP.

LESSONS: We described 2 rare cases of small bowel intussusception caused by IFP. IFP commonly involves only the submucosa, rarely breaks through the submucosa, and invades the muscularis propria and subserosa layer. Its invasive nature is extremely rare and may provide additional evidence to support the neoplastic nature of IFP. Besides, a differential diagnosis is essential When an IFP is negative for CD34 expression.