A 45-year-old woman visited our hospital for further evaluation of fecal occult blood in a yearly physical checkup. Colonoscopy revealed a red peduncular polyp, about 20?mm in diameter, in the sigmoid colon (Figure 1(a)). With conventional colonoscopy, the lesion did not show type III or IV pit pattern although magnifying colonoscopy was not performed. We speculated that this polyp was nonneoplastic. It was suspected to be an inflammatory polyp [IMGP or inflammatory fibroid polyp (IFP)] from endoscopic findings. Excluding the polyp, there was no lesion in the colorectum. Endoscopic polypectomy was performed. Histological examination of the specimen revealed inflammatory granulation tissue in the lamina propria, proliferation of smooth muscle, and hyperplastic glands with cystic change.

A 50-year-old man visited our hospital for further evaluation of fecal occult blood in a yearly physical checkup. Colonoscopy revealed a red, hard peduncular polyp, about 20 mm in diameter, in the descending colon (Figure 1(b)). Magnifying observation (EC-450ZH, Fujinon Toshiba ES Systems) showed type I or II pit pattern (Figure 2(a)). We speculated that this polyp was nonneoplastic. It was suspected to be an inflammatory polyp from endoscopic findings although it should be distinguished from a juvenile polyp. Endoscopic polypectomy was performed. Histological examination of the specimen revealed inflammatory granulation tissue in the lamina propria, proliferation of smooth muscle, and hyperplastic glands with cystic change (Figures 4(a) and 4(b)).

A 49-year-old man consulted a physician for further evaluation of fecal occult blood in a yearly physical checkup. Colonoscopy revealed a red, hard, spherical peduncular polyp with erosion and mucous exudation, about 20?mm in diameter, in the sigmoid colon (Figure 1(c)). Magnifying observation (EC-450ZH, Fujinon Toshiba ES Systems) revealed a red, slightly rugged surface consisting of an aggregation of smooth nodules (Figure 2(b)) with some normal round crypt openings (Figure 2(c)). We speculated that this polyp was nonneoplastic. It was suspected to be an inflammatory polyp from endoscopic findings although it should be distinguished from a juvenile polyp. An air contrast barium enema also revealed a pedunculated polyp like a snowman shape in the sigmoid colon (Figure 3). Endoscopic polypectomy was performed. Histological examination of the specimen revealed inflammatory granulation tissue in the lamina propria, proliferation of smooth muscle, and hyperplastic glands with cystic change (Figures 4(c) and 4(d)).

A 78-year-old man consulted a physician for further evaluation of fecal occult blood in a yearly physical checkup. Colonoscopy revealed a red, hard, conic peduncular polyp, about 20 mm in diameter, in the ascending colon (Figure 1(d)). With conventional colonoscopy, the lesion did not show type III or IV pit pattern. Magnifying observation (EC-450ZH, Fujinon Toshiba ES Systems) revealed a red, slightly rugged surface consisting of an aggregation of smooth nodules (Figure 2(d)). We speculated that this polyp was nonneoplastic. It was suspected to be an inflammatory polyp (IMGP or IFP) from endoscopic findings. Excluding the polyp, there was no lesion in the colorectum. Endoscopic polypectomy was performed. Histological examination of the specimen revealed inflammatory granulation tissue in the lamina propria, proliferation of smooth muscle, and hyperplastic glands with cystic change.

In most cases, the presenting signs and symptoms of IMGP are nonspecific. In a recent systematic review, Fujino et al. [⁸] described the most common symptoms of patients with IMGP as positive fecal occult blood (29%), and hematochezia (23%); less commonly, patients present with abdominal pain, constipation and anemia [²]. Small IMGPs in the colon are usually asymptomatic and often detected incidentally on barium enema or endoscopy [⁸?¹⁰]. Endoscopic characteristic findings include: (1) pedunculated or semipedunculated, (2) red, and (3) smooth, spherical, and hyperemic surface with patchy mucous exudation and erosion [⁸, ⁹]. It is difficult to distinguish IMGPs from juvenile polyps [¹³, ¹⁴] or inflammatory fibroid polyps [¹⁵, ¹⁶] according to endoscopic findings (Table 1). It is necessary to distinguish IMGPs from juvenile polyps because juvenile polyps sometimes recur after endoscopic resection [¹⁷] and recently juvenile polyps are suspected that they have neoplastic potential [¹⁸].

Moriyama et al. reported magnifying endoscopic findings of 5?IMGPs in 2003 [⁹]. They described that magnifying observation revealed a slightly rugged surface consisting of aggregated smooth nodules with enlarged round or oval crypt openings. In case 3 and case 4, magnifying endoscopic findings were the same as Moriyama's description. However, in case 2, enlarged round or oval crypt openings were found; however, aggregated smooth nodules were not seen. We had once reported a unique lobulated IMGP that had a red, slightly rugged surface component without normal mucosal structure and smooth white nodules with enlarged round or oval crypt openings [¹¹]. There have been few reports on magnifying endoscopic findings of IMGP. To clarify the characteristic magnifying endoscopic findings of IMGP, we should accumulate and analyze many cases of IMGP.

IMGP is characterized by inflammatory granulation tissue in the lamina propria, proliferation of smooth muscle, and hyperplastic glands with variable cystic changes. Histological findings of IMGP are similar to those of juvenile polyp [¹⁴]. The diagnosis of colorectal IMGPs could seldom be made by endoscopic biopsy and the final diagnosis of colonic IMGP depends on the pathological findings of EMR or endoscopic polypectomy specimens because the biopsy is often not deep enough to obtain the tissue showing proliferation of smooth muscle or hyperplastic glands with variable cystic changes.

There have been few reports on barium enema characteristic findings of IMGP. We had once reported radiographic findings of 2?IMGP cases [¹¹, ¹²]. An about 40?mm in diameter, pedunculated, lobulated polyp located in the ascending colon in one case [¹¹], and an about 20?mm in diameter, spherical peduncular polyp located in the descending colon in another case [¹²]. We showed four new IMGP cases in this literature, and presented a radiographic finding of an about 20?mm in diameter, pedunculated polyp like a snowman shape, located in the sigmoid colon in case 3.

IMGP of the large intestine can best be removed endoscopically, because it is thought to be clinically and histologically benign. IMGP has never been reported to accompany neoplasia to date [⁷]. Most Japanese cases have been treated with polypectomy or endoscopic mucosal resection (EMR) [⁵, ⁷?¹²].