Though it’s not a sign found in most patients, when present the accumulation of mast cells in the gastrointestinal (GI) tract can be a strong indicator that a patient has systemic mastocytosis (SM), according to a study published recently in the American Journal of Clinical Pathology.
This study reviewed 104 people ranging from age 1 to 92 who underwent 258 GI biopsies. About one-third of those with SM had GI tissue involvement. Only one person without SM had a positive GI biopsy.
This pattern led to a 95% positive predictive value and 98% specificity, meaning GI mastocytosis almost always signals bone marrow disease, but its absence is common even when the disease is present.
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Nearly two-thirds of affected GI samples were weakly positive or negative for tryptase, an enzyme secreted by mast cells. In bone marrow biopsies, elevated tryptase levels are a sign of SM. The inconclusive tryptase results from the GI samples explains why SM can be missed in GI biopsies and highlights the need for additional stains that can signal SM, such as CD117 and CD25.
These tests found SM in 19 GI biopsy specimens that were originally read as normal. Patients whose GI biopsies showed mastocytosis also had notably higher serum tryptase levels.
“When GI biopsy specimens are obtained due to SM-related GI symptoms, caution is needed when the mast cell infiltrates are sparse or lack compact aggregates,” explained this study’s authors. “Immunohistochemistry for tryptase may have limited sensitivity.”
Advanced genetic testing added further clarity. Using droplet digital PCR, doctors found the KIT D816V mutation in 12 of 13 mastocytosis-positive GI biopsy samples with enough DNA. This method outperformed a traditional test, particularly when the number of abnormal cells was low. For patients, this means that even small tissue samples may still provide crucial answers.
Symptoms prompting biopsies included abdominal pain, diarrhea, vomiting, reflux, bleeding or evaluation of polyps. The results show that when mast cells gather in the gut, they can form dense clusters or spread more subtly, which influences how easily they are detected.
Overall, the study underscores the importance of specialized testing to diagnose mastocytosis accurately. For patients, improved testing can lead to earlier identification, clearer treatment decisions, and better understanding of symptoms that may otherwise seem unexplained.
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