Practical and reproducible estimation of myenteric interstitial cells of Cajal in the bowel for diagnostic purposes

Background Histological assessment of the interstitial cells of Cajal (ICCs) in the bowel is important for diagnosing patients with gastrointestinal neuromuscular diseases (GINMD). Although the International Working Group on GINMD proposed reporting a decrease in ICC number of more than 50%, quantitative methods used in literature are not practical for daily routine of the pathologist. Consequently, this study presents a straightforward semiquantitative estimation method for myenteric ICCs of the bowel. Methods Formalin-fixed paraffin-embedded sections from small bowel (n = 87) and colon (n = 159) were collected to create two control groups and four groups composed of patients with gastrointestinal motility disorders. The control groups included material of resection and autopsy origin, respectively. Samples were stained with CD117 (c-kit) antibody to estimate the myenteric ICC network. Scores of two observers were compared to analyze inter-and intraobserver agreement and reliability. Key Results Interobserver reliability was almost perfect for small bowel (intraclass correlation coefficient 0.847; 95% confidence interval [CI]: 0.774-0.897) and substantial for colon (0.683; 95% CI: 0.591-0.758). Almost perfect intraobserver reliability was found (intraclass correlation coefficient 0.918; 95% CI: 0.874-0.947). The small bowel showed more myenteric ICCs than the colon. Neither significant differences between colonic regions were found nor were there any differences in the orientation of the sections. Conclusions & Inferences The proposed estimation method for the myenteric ICC network showed generally good agreement and reliability. As the method is semi-quantitative, simple, and capable to differentiate between normal and diseased tissue, it can be used in routine diagnostics of gastrointestinal neuromuscular disorders.