Inflammatory myoglandular polyp of the cecum: case report and review of literature.

BACKGROUND
Inflammatory myoglandular polyp (IMGP) is a rare non-neoplastic polyp of the large bowel, commonly with a distal localization (rectosigmoid), obscure in its pathogenesis. Up till now, 60 cases of IMGP have been described in the literature, but none located in the cecum.


CASE PRESENTATION
We report a case of a 53-year-old man who was admitted to our hospital for further evaluation of positive fecal occult blood test associated to anemia. A colonoscopy identified a red, sessile, lobulated polyp of the cecum, 4.2 cm in diameter, partially ulcerated. The histological examination of the biopsy revealed the presence of inflammatory granulation tissue with lymphocytic and eosinophil infiltration associated to a fibrous stroma: it was diagnosed as inflammatory fibroid polyp. Considering the polyp's features (absence of a peduncle and size) that could increase the risk of a polypectomy, a surgical resection was performed. Histological examination of the specimen revealed inflammatory granulation tissue in the lamina propria, hyperplastic glands with cystic dilatations, proliferation of smooth muscle and multiple erosions on the polyp surface: this polyp was finally diagnosed as IMGP. There was also another little polyp next to the ileocecal valve, not revealed at the colonoscopy, 0.8 cm in diameter, diagnosed as tubulovillous adenoma with low grade dysplasia.


CONCLUSIONS
This is the first case of IMGP of the cecum. It is a benign lesion of unknown pathogenesis and must be considered different from other non-neoplastic polyps of the large bowel such as inflammatory cap polyps (ICP), inflammatory cloacogenic polyps, juvenile polyps (JP), inflammatory fibroid polyps (IFP), polyps secondary to mucosal prolapse syndrome (MPS), polypoid prolapsing mucosal folds of diverticular disease. When symptomatic, IMGP should be removed endoscopically, whereas surgical resection is reserved only in selected patients as in our case.


Case presentation
A 53-year-old man was admitted to our hospital for further evaluation of anemia (haemoglobin concentration 10,6 g/dl, RBC 2.970.000/mm 3 , HTC 31,4%) associated to positive fecal occult blood test. He had been treated for an autoimmune haemolytic anemia 4 years before, but immuno-haematological tests excluded signs of haemolysis. He also had an autoimmune thyroiditis. He had neither bleeding from rectum nor diarrhea or other gastrointestinal symptoms. Abdominal examination was negative. Rectal exploration did not reveal any pathological sign. A colonoscopy identified the presence of a spherical, sessile, lobulated polyp of the cecum, 4.2 cm in diameter, with a red and not bleeding but partially ulcerated surface (figure 1). Because of the absence of a peduncle and its large size, the endoscopist decided to perform a biopsy of the polyp rather than a polypectomy. The histological examination of the specimen revealed the presence of inflammatory granulation tissue with lymphocytic and eosinophil infiltration associated to a fibrous stroma: it was diagnosed as inflammatory fibroid polyp [15]. Considering the chronic anemia and the polyp's features (absence of a peduncle and size), we decided to perform an ileocecal resection with a laterolateral ileocolic anastomosis (figure 2). The histological examination of the polyp revealed inflammatory granulation tissue and engorged capillaries in the lamina propria, hyperplastic glands with cystic dilatations, proliferation of smooth muscle and multiple erosions on the polyp surface ( figure 3). There was not superficial fibrin exudation. According to these features [1] it was finally diagnosed as inflammatory myoglandular polyp (IMGP). There was also another little polyp next to the ileocecal valve, not revealed at the colonoscopy, 0.8 cm in diameter, diagnosed as tubulovillous adenoma with low grade dysplasia. The patient was discharged from our hospital four days after the operation without any postoperative complications. After two months the patient has good health and anemia was resolved.
The final diagnosis of IMGP is achieved by histological examination through endoscopic mucosal resection (EMR) or polypectomy, whereas the simple biopsy alone is not enough for a correct diagnosis as in our case. Some authors [8,12] reported a correlation between the characteristic surface of the polyp under magnifying endoscopy and its histological features. As their experience is limited to 10 patients more cases should be studied.
IMGP must be differentiated from other non-neoplastic polyps such as inflammatory cap polyps (ICP), inflammatory cloacogenic polyps, juvenile polyps (JP), inflammatory fibroid polyps (IFP), polyps secondary to mucosal prolapse syndrome (MPS), polypoid prolapsing mucosal folds of diverticular disease [6]. Bathal et al. [14,16] consider IMGP and all these lesions as part of a same group with small histological variations and as result of prolapse. However, we agree with others [1,[9][10][11][12][13][14][15][16][17][18] who consider IMGP as a distinct entity. In fact, each type of these polyps presents both histological and clinical differences from the IMGP. Inflammatory cap polyps (ICP) are usually multiple, sessile, covered by a fibrin cap and associated with inflammatory bowel diseases or colonic cancer [19]. Moreover the common symptoms of ICPs are mucous diarrhea and tenesmus, and they usually develop in the rectosigma. Inflammatory cloacogenic polyps are solitary, peduncolated, with tubulovillous architecture and localized only at the anorectal transition zone [20]. Juvenile polyps do not show proliferation of the muscolaris mucosae and develop in young age [1]. Inflammatory fibroid polyps (IFP) mostly occur in stomach and small bowel and are histologically characterized by connective tissue with abundant inflammatory cells, in particular plasma cells and eosinophils [15]. IMGP should not be also considered as polyps secondary to mucosal prolapse syndrome or as polypoid prolapsing mucosal folds of diverticular disease. In the former, polypoid lesions are usually villous, granular or cauliflower-like, frequently found in females and in older patients than IMGPs [1]. In the latter, no correlation between IMGP and diverticular disease has been found [21].
Concerning therapy, endoscopic treatment of IMGP is the gold standard because it is clinically and histologically benign as reported in literature [1][2][3][4][5][6][7][8][9][11][12][13], with the exception of Kayhan et al. [10] who performed a left hemicolectomy because of the polyp size (> 6 cm). We also decided for surgical resection because of increased risk of endoscopic polypectomy (bleeding and perforation) related to polyp diameter and the absence of a peduncle. However we agree with authors who consider that the number of surgical resections for colonic IMGP will decrease and endoscopic resection will increase in the future considering the recent advances of the diagnostic and therapeutic endoscopy [12,13].
The causes of IMGP are still unclear. Nakamura et al. [1] think that chronic trauma from the fecal stream and from peristalsis may have a role in its pathogenesis. This theory came from the observation that IMGP were found only in the left colon where the feces are solid and more able to injure the colonic mucosa [1,8]. Nevertheless, recent papers described IMGPs in the proximal transverse [7,11] and ascending colon [12] or in the cecum as we found.

Conclusion
We reported the first case of sessile and lobulated IMGP of the cecum. Concerning its benign biology, it should be removed endoscopically when it is symptomatic (hemorrage, occlusion). Surgical treatment is reserved only in selected cases. It must be considered different from other non-neoplastic polyps for its clinical and histopathological features. More studies are required to understand its pathogenesis.

Consent
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal