Clinical history: 50 year old female with diarrhea, 5-8 bowel movements per day, abdominal pain, lasting > 1 year.
Questions: What is the diagnosis, the main differential, and key gross, histologic and clinical features to distinguish the two?
What is the most probable diagnosis?
As with case 1, this specimen represents inflammatory bowel disease (IBD), with the differential between Crohn's colitis and ulcerative colitis.
On low power, it is apparent that the disease is diffuse, and confined to the mucosa and muscularis mucosa, with no involvement of the muscularis propria, and these features are consistent with ulcerative colitis.
There is architectural distortion including crypt branching. There are many granulomas present, however they are all associated with damaged crypts with leakage of mucin (mucin granulomas), a diagnostic pitfall for the granulomas seen in Crohn's disease. Cryptitis and crypt absecesses are seen in both Crohn's and ulcrative colitis, therefore mucin granulomas cannot be used to distinguish between the two.
Another important feature of this case is the involvement of the appendix, presence of cecal inflammation and adjacent ileitis, with the bulk of disease in the left colon. This represents an atypical presentation of ulcerative colitis, which is often misdiagnosed as a skip lesion in Crohn's colitis. The following list (Odse, 2003), summarizes unusual patterns of disease in ulcerative colitis:
Low grade disease in remission
Cecum/ascending colon inflammation in left-sided colitis
Pediatric UC (initial presentation)
Rare UGI involvement (i.e., duodenitis)
Odse R. Diagnostic Problems and Advances in Inflammatory Bowel Disease. Mod Pathol 2003;16(4):347–358