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Although there have been only 15 published case reports of enteritis cystica profunda, the condition is frequently seen by pathologists. Its importance lies in the resemblance to bowel adenocarcinoma.
A man of 33 with a history of suspected Crohn’s disease was admitted after the acute onset of painful abdominal distension. A 15 cm mass was palpable in the suprapubic region and a CT scan showed multiple abdominopelvic fluid collections. He deteriorated on conservative management and an exploratory laparotomy was performed. Around 3 L of pus was drained from collections formed within the pelvis and in the paracolic gutters, anterior abdominal wall and loops of bowel. As the terminal ileum was thickened and adherent to omentum, a presumptive diagnosis of a sealed ileal perforation was made. A right hemicolectomy with resection of distal ileum was performed and an end ileostomy and mucous fistula were fashioned. The ileostomy was reversed a year later and he was in good health 4 years postoperatively.
The serosal surface of the resected specimen was covered by a purulent, fibrinous exudate and a 1.5 cm diameter stricture was seen in the terminal ileum. Proximal to the stricture, multiple cystic lesions (0.3–0.6 cm) were noted within the subserosa, the muscularis propria and the submucosa, causing thickening and distortion of the ileal wall. Most were filled with mucinous material although some contained purulent fluid. The distal terminal ileum, large bowel and appendix were macroscopically normal.
Microscopically the cysts were partially lined by columnar epithelium and distended by periodic-acid/Schiff-positive mucinous material (Figure 1). They were surrounded by a chronic inflammatory cell reaction and fibrosis, but no dysplastic features were noted. There were foci of disruption and thickening of the muscularis mucosae, suggesting previous ulceration, possibly as a result of Crohn’s disease.
In enteritis cystica profunda the mucin-filled cysts in the bowel wall outside of the mucosal layer1 are thought to arise after mucosal ulceration or inflammatory damage to the submucosa has allowed outgrowth of epithelial elements into the other layers of the bowel wall.2 These ectopic epithelial elements frequently lack a continuous epithelial lining and are usually surrounded by an inflammatory cell infiltrate. Other features can include calcifications, fibrosis and ossified deposits within the mucin lakes.
Enteritis cystica profunda is a benign entity and similar changes can be found anywhere along the gastrointestinal tract.3 In the colon it can mimic invasive adenocarcinoma, especially when the ectopic mucosal elements occur within large dysplastic sigmoid colon adenomas. In our patient, invasive adenocarcinoma was unlikely for two reasons. First, adenocarcinoma of the small bowel is exceedingly uncommon and, secondly, no dysplastic features were noted.
Histological criteria for differentiating epithelium displacement (pseudoinvasion) from true invasion in colorectal tissue have been established4 but individual cases can pose diagnostic difficulties. Immunohistochemical stains (Ki-67, urokinase plasminogen activator receptor, MMP-1, p53, E-cadherin and collagen IV) offer an adjunct to conventional histopathological description.5,6