A Case of Inflammatory Fibroid Polyp with an Elongated Shape in Cecum

A 65‐year‐old woman had mild paroxysmal pain in the upper abdomen for 3 years. A colonic endoscopy performed in Taizhou People’s Hospital found a cylindrical elongated, worm‐like polyp with a narrow base in the cecum [Figure 1a]. The surface mucosa of the polyp showed multifocal erosion [Figure 1b]. No diverticulum, other polyps or mass were found during endoscopy. She subsequently underwent endoscopic resection of the polyp. Macroscopically, the resected sample consisted of a light pink, cylindrical, long‐strip polypoid mass with a size of 100 mm × 8 mm. It had a mucosal surface and was nodular with a narrow base [Figure 1c]. The mucosa showed several small focal, dark red hemorrhages. Microscopically, the cylindrical polyp had a three‐layer structure, with a mucosal surface covering the large bowel mucosa, mutilated muscularis mucosae, and submucosa in the stalk. The covering of mucous membrane was similar to normal colon mucosa and showed slight local thinning and mucosa lamina propria bleeding, which corresponded to the observed gross mucosal dark red area of hemorrhage. The submucosa was expanded and contained dilated and distorted lymphatic and blood vessels running in parallel with the long axis of the polyp [Figure 2a]. The veins were thick‐walled and fibrous tissue hyperplasia was easily seen including numerous thin spindle cells wrapped around small blood vessels in an onionskin‐like concentric pattern. In the mucosal and submucosal layers, moderate inflammatory cell infiltration was observed, including lymphocytes, plasma cells, and eosinophils, and occasionally lymphoid follicles in the deep lamina propria [Figure 2b and 2c]. Immunohistochemical analysis showed that the spindle cells in the submucosal were positive for CD34 [Figure 3a] and negative for CD117, platelet‐derived growth factor receptor‐alpha (PDGFRA) [Figure 3b], DOG‐1, S‐100 protein, desmin, smooth muscle actin, fascin, and CD35. Ki‐67 staining was <2%, indicating a very low proliferative index. The lymphocytes were mainly CD20‐positive B cells and appeared in the lamina propria. Genetic analysis indicated a V824V synonymous point mutation in exon 18 A Case of Inflammatory Fibroid Polyp with an Elongated Shape in Cecum