Evaluation of intestinal biopsies for pediatric enteropathy: a proposed immunohistochemical panel approach.

Congenital enteropathies are rare disorders with significant clinical consequences; however, definitive diagnosis based on morphologic assessment of duodenal biopsies with routine stains alone is often impossible. To determine the role of immunohistochemistry (IHC) in the evaluation for microvillous inclusion disease, congenital tufting enteropathy (intestinal epithelial dysplasia), and enteroendocrine cell dysgenesis, a series of duodenal biopsies from 26 pediatric patients with chronic/intractable diarrhea was retrospectively reviewed. IHC stains for CD10, EpCAM, chromogranin, and villin were performed on all biopsies, and the results were correlated with hematoxylin and eosin and ultrastructural findings using electron microscopy, when available. Biopsies from 2 patients diagnosed with microvillous inclusion disease at the time of original biopsy demonstrated diffuse CD10-positive cytoplasmic inclusions within enterocytes and normal expression of EpCAM and chromogranin. Biopsies from 3 patients, including 2 siblings with confirmed EPCAM mutations, demonstrated complete loss of EpCAM expression and normal expression of CD10 and chromogranin; electron microscopic evaluation revealed characteristic ultrastructural findings of tufting enteropathy. Biopsies from 1 patient with a confirmed NEUROG3 mutation demonstrated an absence of intestinal enteroendocrine cells by chromogranin staining, consistent with enteroendocrine cell dysgenesis. Four patients' biopsies displayed nonspecific staining patterns for CD10 and/or EpCAM with normal expression of chromogranin, and 16 patients' biopsies exhibited normal expression for all 3 markers. Villin stains demonstrated heterogenous brush border labeling with nonspecific cytoplasmic reactivity, a pattern variably present throughout the biopsy series. In conclusion, the routine use of an IHC panel of CD10, EpCAM, and chromogranin is warranted in patients meeting specific age and/or clinical criteria, as the morphologic findings of congenital enteropathies may be subtle, focal, or inapparent on routine stains.