Haider Mejbel, M.D.

Haider A. Mejbel, M.D., is a gastrointestinal, hepatobiliary, and molecular pathologist with expertise in precision oncology, molecular diagnostics, and digital pathology. His academic and clinical work integrates histopathology, genomic profiling, and emerging artificial intelligence technologies to advance personalized cancer diagnosis and treatment.

Dr. Mejbel investigates the genomic landscape of gastrointestinal and hepatobiliary malignancies — including gastrointestinal stromal tumors, cholangiocarcinoma, colorectal carcinoma, and pancreatic ductal adenocarcinoma — to identify actionable therapeutic targets and refine risk stratification, with particular attention to how specific alterations influence prognosis and treatment selection. In parallel, he develops and validates deep learning models that predict molecular status, grade dysplasia, and forecast therapeutic response directly from tissue morphology, with applications in colorectal carcinoma, Barrett's esophagus, inflammatory bowel disease, and liver transplant biopsies.

His research also examines predictive biomarkers of the tumor microenvironment, including PD-L1 expression, mismatch repair status, tumor mutation burden, and the spatial architecture of tumor-infiltrating lymphocytes. He maintains an active interest in the molecular genetics of sarcoma and bone tumors, where he characterizes novel genomic alterations that may alter disease classification and inform therapy. Much of this work is conducted through multi-institutional, multidisciplinary collaborations pairing pathologists with gastroenterologists, oncologists, surgeons, and computational scientists.

• Gastrointestinal and hepatobiliary cancer diagnosis. Cancers of the digestive tract, liver, bile ducts, and pancreas remain among the leading causes of cancer death. Dr. Mejbel diagnoses these tumors from tissue biopsies and surgical specimens, establishing the precise classification and staging that determine each patient's treatment options.
• Genomic profiling of solid tumors. Dr. Mejbel investigates molecular alterations in solid tumors. He uses next-generation sequencing, ribonucleic acid (RNA) fusion profiling, fluorescence in situ hybridization (FISH), and single-gene testing to identify genetic changes that predict response to targeted therapy and guide personalized treatment decisions.
• Inflammatory bowel disease and liver transplantation. Dr. Mejbel evaluates biopsies from patients with ulcerative colitis, Crohn's disease, and liver allografts, assessing disease activity, detecting early dysplasia, and grading rejection.
• Cancer immunotherapy biomarkers. Dr. Mejbel studies tissue-based predictors of immunotherapy response, including PD-L1 immunohistochemistry, mismatch repair and microsatellite instability status, tumor mutation burden, and the spatial distribution of tumor-infiltrating lymphocytes. These markers help identify which patients are most likely to benefit from immunotherapy.
• Computational pathology. Dr. Mejbel is interested in the development of computational pathology, digital pathology, and machine learning using pathology images and molecular databases. These fields will improve diagnostic accuracy and reproducibility, streamline pathology workflow, and ultimately benefit patient care.