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Performing colonic mast cell counts in patients with chronic diarrhea of unknown etiology has limited diagnostic use
Aisha Sethi1, Dhanpat Jain, Bani Chander Roland
1From the Department of Pathology (Drs Sethi and Hanson) and the Clinical and Translational Science Center (Dr Schrader), University of New Mexico School of Medicine, Albuquerque; the Departments of Pathology (Drs Jain and Gibson) and Internal Medicine, Section of Digestive Diseases (Dr Kinzel), Yale University School of Medicine, New Haven, Connecticut; and the Department of Internal Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins School of Medicine, Baltimore, Maryland (Dr Roland).
Context:
Mastocytic enterocolitis is a recently described entity defined by chronic diarrhea of unknown etiology and normal colon biopsy results with increased mast cells (MCs) seen on special stains. These patients may benefit from mast cell stabilizers; however, the clinical utility of MC counts remains unknown.
Objective:
To determine the clinical utility of colonic MC counts on normal biopsies in patients with chronic diarrhea of unknown etiology.
Design:
Blinded MC counts using a c-Kit stain were performed in 76 consecutive patients with chronic diarrhea of unknown etiology who had normal colon biopsy results and in 89 consecutive control patients presenting for screening colonoscopy. Mast cells were counted per single high-power field in the highest-density area. A t test was used to compare the counts, and receiver operating characteristic curves were generated to examine sensitive and specific cutoff values.
Results:
Overall, MC counts averaged 31 MCs per high-power field in the study group versus 24 MCs per high-power field in the control group (P < .001). When stratified by location, a significant increase was seen in biopsies from the left colon only. Receiver operating characteristic analysis revealed that overall MC counts, left-sided MC counts, and the difference between right- and left-sided MC counts did not yield discriminatory cutoff values (area under the curve, 0.68, 0.74, and 0.81, respectively).
Conclusions:
Mast cell counts were increased in patients with chronic diarrhea of unknown etiology, primarily in the left colon. However, receiver operating characteristic analysis demonstrates no discriminatory cutoff values. Quantitative MC stains yield little useful diagnostic information, and further studies are necessary to determine whether mastocytic enterocolitis truly represents a distinct entity.
Insights
Increased mast cells (MCs) in the colon are linked to chronic diarrhea. However, quantitative MC counts on biopsies lack diagnostic value for mastocytic enterocolitis, requiring further research.
Area of Science:
- Gastroenterology
- Histopathology
- Immunology
Background:
- Mastocytic enterocolitis is a newly identified condition characterized by chronic diarrhea and increased colonic mast cells (MCs) on special stains.
- The diagnostic utility and clinical significance of elevated MC counts in normal colonic biopsies for chronic diarrhea remain unclear.
- Mast cell stabilizers may benefit patients, but objective diagnostic criteria are needed.
Purpose of the Study:
- To evaluate the clinical utility of quantifying colonic mast cells (MCs) in patients presenting with chronic diarrhea of unknown etiology and normal colon biopsy results.
- To determine if MC counts can serve as a discriminatory diagnostic marker for a potential mastocytic enterocolitis entity.
Main Methods:
- A blinded analysis of c-Kit stained colonic biopsies was performed on 76 patients with chronic diarrhea and 76 control subjects undergoing screening colonoscopy.
- Mast cells were quantified per high-power field in the highest-density area.
- Statistical analysis included t-tests and receiver operating characteristic (ROC) curve analysis to assess diagnostic cutoff values.
Main Results:
- Colonic MC counts were significantly higher in patients with chronic diarrhea (31 MCs/HPF) compared to controls (24 MCs/HPF) (P < .001).
- This increase was predominantly observed in left-sided colon biopsies.
- ROC analysis indicated that neither overall MC counts, left-sided MC counts, nor the difference between right- and left-sided counts provided reliable discriminatory cutoff values (AUCs 0.68–0.81).
Conclusions:
- While MC counts are elevated in patients with chronic diarrhea, particularly in the left colon, they do not offer sufficient discriminatory power for diagnosis.
- Quantitative mast cell staining on routine biopsies provides limited diagnostic information for mastocytic enterocolitis.
- Further investigation is essential to establish mastocytic enterocolitis as a distinct clinical entity and define its diagnostic criteria.
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