Introduction

Localized giant pseudopolyposis is an interesting but extremely rare feature of pseudopolyposis complicating ulcerative colitis or Crohn's disease. The lesion represents a localized exuberant collection of pseudopolyps giving rise to a large discrete intraluminal colonic mass, wich may simulate neoplasms such as villous adenoma or polypoid cancer.

Its diagnosis should be suspected whenever a villous-like or multinodular polypoid mass develops in a patient with known colitis, or when such an intraluminal mass is seen in association with radiological or endoscopic changes of diffuse or segmental inflammatory disease elsewhere in the colon.

Case Report

A 50 year old man, with a 10 year history of pancolonic ulcerative colitis under medical treatment, presented with symptoms of subacute large bowel obstruction. At colonoscopy a large polypoid lesion was observed in the distal transverse colon, causing almost complete luminal obstruction. Mucosal biopsies demonstrated chronic ulcerative colitis changes and multiple hyperplastic pseudopolyps with active inflammation findings. In abdominal CT scan an obstructive thickening of the distal transverse colon, just before the splenic flexure, was seen, with the question of malignancy.

During the time of diagnostic investigation, the patient established complete obstruction and was operated on. Intraoperatively a large neoplastic mass was found to be the cause of obstruction and total colectomy with ileorectal anastomosis was performed. The giant polypoid mass was located in the distal transverse colon and extended circumferentially in a distance of 15cm, causing almost complete luminal obstruction (Figure 1, 2). Its macroscopic features were highly suspicious of malignancy. Two more solitary polypoid lesions were found in the surgical specimen (Figure 1: A, B). The first one (A), with greater diameter of 0,5cm, was located in a distance of 6cm and, the second one (B), sized 2,5x0,4cm, in a distance of 46cm from ileocecal valve. The sigmoid colon did not appear significant macroscopic changes.

Figure 1

Figure 1: Surgical Specimen: The giant polypoid mass located in the distal transverse colon, causing almost complete luminal obstruction. Solitary polypoid lesion (A), with greater diameter 0,5cm, in a distance of 6cm from ileocecal valve. Solitary polypoid lesion (B), sized 2,5x0,4cm,.in a distance of 46cm from ileocecal valve

Figure 2

Figure 2: Surgical Specimen: The giant polypoid mass

The microscopic examination confirmed the diagnosis of localized giant pseudopolyposis revealing multiple pseudopolyps on a background of active ulcerative colitis changes, with cryptitis, cryptic abcesses and ulcers and, pyogenic serositis with intense fibroblastic stroma reaction (Figure 3, 4).

Figure 3

Figure 3: Microscopy: Excessive active ulcerative colitis changes with cryptitis, cryptic abcesses and ulcers (H-E X200)

Figure 4

Figure 4: Microscopy: Multiple pseudopolyps with dense inflammatory monocyte infiltrations of mucosa extended to submucosa and partly to muscularis propria, and intense regenerative activity of lining glandular epithelium (H-E X400)

The pseudopolyps presented dense inflammatory monocyte infiltrations of mucosa extended to submucosa and partly to muscularis propria, as well as intense regenerative activity of lining glandular epithelium. The solitary polypoid lesions were found to be a villous adenoma with mild dysplasia the first (A) and, a pseudopolyp the second (B). Multiple sections from sigmoid colon demonstrated some small pseudopolyps and, disturbance of glandular architecture and cell synthesis with mucosal swelling. The patient's postoperative recovery was uneventful.

Discussion

Pseudopolyposis is probably the most common local complication of ulcerative colitis₁. The reported incidence varies from 12,5% to 74%, depending on the diagnostic criteria employed and patients groups studied₁, ₂. Pseudopolyps represent polypoid edematous mucosal tags, regenerative mucosal islands between areas of ulceration or heaped-up granulation tissue covered by glandular epithelium (Dukes, 1954). They may be seen in the active or quiescent phase of the disease and can be diffuse or local in distribution. There is a direct relation between severity and extension of the disease and the incidence of pseudopolyposis, although the outcome of severe attacks of ulcerative colitis in the presence of pseudopolyps has been found to be more favourable₂. The majority of evidence supports the concept that pseudopolyposis per se is not a precancerous change and the discovery of pseudopolyps in itself does not require any specific treatment₁, ₂.

Although pseudopolyps are the commonest sequelae of ulcerative colitis, the occurrence of localized exuberant collections of pseudopolyps, giving rise to large intraluminal masses, is a rare finding during the course of the disease₃. The term ‘‘Localized giant pseudopolyposis'‘ has been applied to describe this phenomenon.

Localized giant pseudopolyposis may occur at any site in the colon, but only 1 case has been recorded in the rectum₃,₄,₅,₆,₇. The lesion is composed of numerous free and interconnecting villous or frond-like mucosal excrescences, is usually circumferential and may be as much as 12-15cm in length.

There are no specific clinical symptoms or physical findings. Localized giant pseudopolyposis may be associated with a wide variety of symptoms such as diarrhea, rectal bleeding, abdominal pain, fever, anemia and weight loss. Most of these symptoms are probably the result of the inflammatory bowel disease rather than symptoms related per se to the localized exuberant mass of pseudopolyps₃. The lesion is sometimes an incidental finding of routine radiological or endoscopic follow-up in patients with long-standing colitis₃. A palpable intraabdominal mass may be found on physical examination in some cases₃. Large bowel obstruction, as in our patient, is a very unusual type of clinical presentation₄.

Localized giant pseudopolyposis on barium enema examination typically appears as a large mass projecting into the lumen of the colon with numerous frond-like excrescences, although in some patients the mass has a more discrete villonodular, polypoid configuration₃, ₆. Motility of fronds may be appreciated on fluoroscopic examination₃.

Apart from large fecal masses, the major conditions which may simulate localized giant pseudopolyposis are polypoid neoplasms such as polypoid cancer, villous adenoma and lymphoma.

Localized giant pseudopolyposis complicating ulcerative colitis can be difficulty differentiated from large bowel polypoid cancer on the basis of preoperative radiological and endoscopic, or even intraoperative findings, although cancer complicating ulcerative colitis usually presents as a constricting anaplastic infiltrative or ulcerative lesion and rarely as an intraluminal polypoid mass₃. However, since polypoid cancer may occur as a complication of chronic inflammatory disease of the colon, it must always be seriously considered in the differential diagnosis of localized giant pseudopolyposis.

In some cases, as in ours, the differentiation between these two lesions cannot be made with any confidence and, extended surgical resection is mandatory, since meticulous histological examination of the resected specimen is probably the only way to exclude the possibility of malignancy and confirm the diagnosis₃.

Although villous adenoma is not a recognised complication of ulcerative colitis, the radiological and endoscopic appearances of localized giant pseudopolyposis and villous adenoma may be very similar, especially when the latter exhibits prominent frond-like excrescences₃, ₆ This type of appearance, however, is generally restricted to rectal villous adenomas and, as it is known, only 1 case of localized giant pseudopolyposis has been reported in the rectum. In the remainder of the colon, villous adenomas tend to have a more polypoid or lobulated appearance and rarely involve the entire circumference of the bowel wall.

Colonic lymphoma or lymphosarcoma may rarely present as an intraluminal polypoid mass and should be included in the differential diagnosis₃, ₆.

Histopathological findings of localized giant pseudopolyposis are essentially those of inflammatory pseudopolyps, consisting of bands of epithelial-lined fibrovascular tissue which project and are limited to the mucosa.

The lining epithelium contains normal or hyperplastic glands without evidence of neoplastic transformation. A mild to moderate degree of associated nonspecific acute and chronic inflammatory cell infiltration is usually present in the lamina propria and submucosa₃,₈.

Correspondence to

Christos A. Papanikolaou 28 Socratus Str. 55134 Kalamaria, Thessaloniki tel – fax : 2310433906 e-mail : ascl@ippokratio.gr