Is IHC Required to Confirm Diagnosis of Jejunal Adenocarcinoma?
Immunohistochemistry (IHC) is not strictly required to diagnose jejunal adenocarcinoma when standard histopathology (H&E staining) clearly demonstrates adenocarcinoma morphology in the appropriate clinical context, but IHC is strongly recommended to confirm the primary site of origin and exclude metastatic disease from other organs, particularly given the rarity of this tumor. 1
Diagnostic Approach for Jejunal Adenocarcinoma
Primary Histopathological Diagnosis
Standard H&E staining is the foundation for diagnosing adenocarcinoma, showing characteristic glandular architecture, cellular atypia, and invasion patterns. 2
For jejunal adenocarcinoma specifically, histopathological examination after surgical resection typically reveals the adenocarcinoma without requiring IHC for the basic diagnosis when morphology is clear. 3, 4
When IHC Becomes Essential
IHC should be performed in jejunal adenocarcinoma cases to:
Confirm intestinal origin using CDX2, which is a highly specific marker for intestinal differentiation and helps distinguish primary small bowel adenocarcinoma from metastatic disease. 1
Exclude metastatic adenocarcinoma from other sites, particularly colorectal, gastric, pancreatic, or gynecological primaries, which can metastasize to the small bowel. 2
Rule out other primary sites when the clinical presentation is atypical, such as when ovarian masses are present (as jejunal adenocarcinoma can metastasize to ovaries). 5
Specific IHC Panel Recommendations
For suspected jejunal adenocarcinoma, the following IHC markers are useful:
CDX2 (positive): Confirms intestinal lineage and is highly specific for gastrointestinal adenocarcinomas. 1
CK20 (typically positive) and CK7 (variable): Help distinguish small bowel from other adenocarcinomas. 2
TTF-1 (negative): Excludes pulmonary adenocarcinoma metastasis. 2
Additional markers as needed based on differential diagnosis, such as ER/PR for gynecological primaries or markers for neuroendocrine differentiation if morphology suggests mixed features. 2
Clinical Context and Pitfalls
Common Diagnostic Challenges
Jejunal adenocarcinoma presents with vague, non-specific symptoms (abdominal pain, weight loss, nausea, vomiting, melena) making preoperative diagnosis difficult and often delayed. 3, 1, 5
Preoperative diagnosis is established in only 50% of cases, with exploratory laparotomy often required for definitive diagnosis. 4, 6
The rarity of jejunal adenocarcinoma (less than 2% of all GI cancers) means it is frequently not considered in differential diagnosis until late stages. 5
When to Prioritize IHC
IHC becomes mandatory rather than optional when:
Poorly differentiated adenocarcinoma is present, making morphological distinction from other primaries impossible on H&E alone. 2
Metastatic disease is present at diagnosis (as in the case with ovarian metastases), requiring confirmation of the primary site. 5
Multiple potential primary sites exist based on imaging or clinical presentation. 2
Biopsy material is limited (from endoscopy or percutaneous biopsy), where tissue preservation is critical but confirmation of origin is essential. 2
Tissue Preservation Considerations
Judicious use of IHC is recommended to preserve tissue for potential molecular testing, particularly in advanced-stage disease where targeted therapies may be considered. 2
Parallel processing of tissue for histology and IHC can shorten turnaround time while ensuring adequate material for all necessary tests. 2
Practical Algorithm
For suspected jejunal adenocarcinoma:
Obtain adequate tissue via surgical resection, laparoscopy with biopsy, or advanced endoscopic techniques (double-balloon enteroscopy). 4, 5
Perform H&E staining first to establish adenocarcinoma diagnosis and assess grade, invasion depth, and lymphovascular involvement. 3, 4
Add IHC panel (CDX2, CK20, CK7, TTF-1 at minimum) if:
Consider additional molecular testing if advanced disease or if targeted therapy options exist. 2