Digestive, hepatic and pancreatic tissue interpretation
Interpret the specimen and pattern
Digestive pathology connects the anatomical site, specimen type, architecture, cell changes, inflammation and clinical context. A superficial mucosal biopsy cannot independently demonstrate every transmural feature seen in a resection. Disease distribution, ulcer pattern, chronic architectural change and granulomas can contribute to an inflammatory bowel differential, but a granuloma alone is not proof of one cause. Celiac assessment considers villous architecture, crypts, intraepithelial lymphocytes, orientation and the relevant serological and dietary context. Subtotal villous atrophy differs from complete flattening within a specified Marsh-Oberhuber framework. Sampling and orientation can create apparent abnormalities that require careful review.
Distinguish injury, repair and invasion
Reactive glands in an inflamed or scarred organ can mimic neoplasia. Cytological atypia is interpreted with growth pattern, relationship to native structures and evidence such as destructive infiltration or perineural invasion. Desmoplasia supports a differential but should not be the sole diagnostic criterion in a severely fibrotic pancreas. Barrett-associated metaplasia, dysplasia and invasive adenocarcinoma represent distinct findings. A high-grade epithelial lesion does not establish depth beyond the sampled tissue. An apparent absence of invasion has meaning only within the actual material examined.
Liver and pancreatobiliary evidence
Hepatocellular, biliary and metastatic tumors require integration of morphology, anatomical distribution and a suitable immunopanel. Arginase, hepatocellular markers, keratins and other stains have limitations; an isolated marker does not establish every primary site. Pancreatic ductal and cholangiocellular tumors can share a keratin profile, so clinical and imaging correlation remains important. Neuroendocrine differentiation, grade and the organ-specific assessment are separate questions. A mucinous pancreatic-cyst assessment does not become a definitive malignant diagnosis from a fluid CEA value alone. In nonneoplastic liver disease, the pattern of duct injury, portal inflammation, fibrosis and deposits helps identify competing causes.
Predictive and inherited-risk assessment
Digestive HER2 scoring is not simply copied from breast scoring. The pattern, specimen type and appropriate assay framework matter, including relevant gastric basolateral or lateral staining. Mismatch-repair staining requires appropriate internal controls. Paired loss can direct a reflex pathway, but MLH1/PMS2 loss alone does not prove Lynch syndrome. BRAF and promoter-methylation assessment have defined roles in colorectal investigation, with family context and specialist genetic evaluation as appropriate. Tissue conservation, representative sampling and accurate reporting support treatment decisions without allowing a biomarker to replace the actual tumor diagnosis.