This duodenal biopsy shows infiltrating irregular glands and blue mucin. Strips of sloughed, relatively benign epithelium are seen on the left.
The tumor extends through the entire bowel wall to involve the subserosal fatty tissues.
The tumor demonstrates poorly formed glands and elaborates blue mucin.
Interestingly, negativity for CDX2 was seen in this tumor. Although 70% of small bowel adenocarcinomas demonstrate CDX2 positivity, poorly differentiated tumors are more likely to be negative for CDX2 (Overman).
This tumor was positive for CK7 and negative for CK20, which is the immunoprofile for the majority (67%) of small bowel adenocarcinomas.
Approximately half of adenocarcinomas in the small bowel occur in the duodenum -- 65% of duodenal adenocarcinomas are located in the periampullary region. The lesions tend to be exophytic and papillary in this region, whereas more distal tumors in the small bowel are more likely to be circumferential and annular (Rosai, Iacobuzio).
Mucin production and CEA reactivity are extremely common in these tumors (Rosai). CK7/CK20 can help differentiate between primary small bowel adenocarcinomas (either CK7+/CK20+ or CK7+/CK20-) versus metastatic colorectal cancer (CK7-/CK20+).
In this particular tumor, the immunoprofile was CK7+ and CK20-, as well as CDX2. CDX2 has proven to be a useful marker for tumors with gastrointestinal differentiation, and is expressed in colorectal tumors and mucinous ovarian tumors. Overman examined 54 small bowel adenocarcinomas and found that 70% of them were CDX2 positive (Overman).
Iacobuzio-Donahue CA, Montgomery EA. Gastrointestinal and Liver Pathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elsevier; 2005: 174-8.
Overman MJ et al. Immunophenotype and molecular characterisation of adenocarcinoma of the small intestine. British Journal of Cancer 102, 144-150 (24 November 2009).
Rosai, J. Rosai and Ackerman's Surgical Pathology. 9th Ed. Philadelphia, PA: Elsevier; 2004: 729.