Reetesh K. Pai, MD
Associate Professor of Pathology

Dr. Pai is an Associate Professor in the Division of Anatomic Pathology, Director of the Gastrointestinal Pathology Center of Excellence, and Director of the Gastrointestinal Pathology Fellowship.

Office Location:
Rm. A610
UPMC Presbyterian Hospital
Pathology Department
200 Lothrop Street
Pittsburgh, PA 15213
Contact Information:
Office Telephone: 412-647-3935


  • MD - 2001, University of New Mexico
  • Surgical Pathology and Cytopathology Fellowships, Stanford University

Clinical Expertise

Dr. Pai is a surgical pathologist and cytopathologist with a subspecialty focus in gastrointestinal/pancreatobiliary pathology at the University of Pittsburgh Medical Center, Presbyterian Hospital. His diagnostic expertise includes neoplastic and non-neoplastic diseases of the colon and rectum, appendix, and pancreas.

Research Interests

Dr. Paiís primary research interests relate to molecular profiling of colorectal, appendiceal, and pancreatic carcinoma and detection of molecular and immunohistochemical biomarkers that have potential to be used clinically for diagnosis, prognostication and treatment of these carcinomas.

Selected Publications

View Dr. Pai's publications on PubMed

  1. Pai RK, Beck AH, Norton JA, Longacre TA. Appendiceal mucinous neoplasms: Clinicopathology study of 116 cases with analysis of factors predicting recurrence. Am J Surg Pathol 2009; 33: 1425-1439.
  2. Munroe CA, Copland A, Pai RK, Friedland S, Triadafilopoulos G. Meckel's diverticulum with gastrointestinal bleeding: role of computed tomography in diagnosis. Dig Dis Sci. 2010; 55:242-244.
  3. Levesque BG, Pai RK, Shah SB. Atypical rectal bleeding: the challenge of diagnosing mild ulcerative colitis. Dig Dis Sci. 2010; 55: 586-8.
  4. Sangoi AR, Karamchandani J, Kim J, Pai RK, McKenney JK. The use of immunohistochemistry in the diagnosis of metastatic clear cell renal cell carcinoma: a review of PAX-8, PAX-2, hKIM-1, RCCma, and CD10. Adv Anat Pathol. 2010;17:377-93.
  5. Chang DT, Chapman CH, Norton JA, Visser B, Fisher GA, Kunz P, Ford JM, Koong AC, Pai RK. Expression of p16(INK4A) but not hypoxia markers or poly adenosine diphosphate-ribose polymerase is associated with improved survival in patients with pancreatic adenocarcinoma. Cancer. 2010; 116:5179-87.
  6. Sangoi AR*, Ohgami RS*, Pai RK, Beck AH, McKenney JK, Pai RK. PAX8 expression reliably distinguishes pancreatic well-differentiated neuroendocrine tumors from ileal and pulmonary well-differentiated neuroendocrine tumors and pancreatic acinar cell carcinoma. Mod Pathol 2011; 24: 412-424.
  7. Pai RK, Beck AH*, Mitchem J, Linehan DC, Chang DT, Norton JA, Pai RK. Patterns of lymph node involvement and prognosis in pancreatic adenocarcinoma: Direct lymph node invasion has similar survival to node-negative disease. Am J Surg Pathol 2011; 35:228-234.
  8. Plerhoples TA, Ahdoot M, Dimaio MA, Pai RK, Park WG, Poultsides GA. Colloid Carcinoma of the Pancreas. Dig Dis Sci. 2011. [Epub ahead of print]
  9. Sharaf RN, Butte AJ, Montgomery KD, Pai RK, Dudley JT, Pasricha PJ. Computational prediction and experimental validation associating FABP-1 and pancreatic adenocarcinoma with diabetes. BMC Gastroenterol. 2011 Jan 20;11:5.
  10. Haynes CM, Sangoi AR*, Pai RK. PAX8 is expressed in pancreatic well-differentiated neuroendocrine tumors and in extrapancreatic poorly differentiated neuroendocrine carcinomas in fine needle aspiration biopsy specimens. Cancer Cytopathol 2011;119: 193-201.
  11. Pai RK, Mojtahed A, and Pai RK. Mutations in the RAS/RAF/MAP kinase pathway commonly occur in gallbladder adenomas but are uncommon in gallbladder adenocarcinomas. Appl Immunohistochem Mol Morphol 2011;19:133-140.
  12. Mojtahed A*, Schrijver I, Ford JM, Longacre TA, Pai RK. A comparable 2-antibody mismatch repair protein immunohistochemistry screening for colorectal carcinomas, skin sebaceous tumors, and gynecologic tract carcinomas. Mod Pathol 2011. 24:1004-1014.
  13. Joshua B, Kaplan MJ, Doweck I, Pai RK, Weissman IL, Prince ME, Ailles LE. Frequency of cells expressing CD44, a Head and Neck cancer stem cell marker: Correlation with tumor aggressiveness. Head Neck 2011; 34:42-49.
  14. Chennupati SK, Quon A, Kamaya A, Pai RK, La T, Krakow TE, Graves E, Koong AC, Chang DT. Positron Emission Tomography for Predicting Pathologic Response After Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer. Am J Clin Oncol 2011. [Epub ahead of print]
  15. Ghole SA, Bakhtary S, Staudenmayer K, Sze DY, Pai RK, Visser BC, Norton JA, Poultsides GA. Ruptured Biliary Cystadenoma Managed by Angiographic Embolization and Interval Partial Hepatectomy. Dig Dis Sci. 2011; 56: 1949-1953.
  16. Dong A, Gupta A, Pai RK, Tun M, Lowe AW. The human adenocarcinoma-associated gene, AGR2, induces expression of amphiregulin through hippo pathway co-activator YAP1 activation. J Biol Chem 2011; 286: 18301-10.
  17. Zhu Y, Colak T, Shenoy M, Liu L, Pai RK, Li C, Mehta K, Pasricha PJ. Nerve Growth Factor Modulates TRPV1 Expression and Function and Mediates Pain in Chronic Pancreatitis. Gastroenterology 2011; 141: 370-377. Pai RK, Jeffrey RB. Pathologic continuum of acute appendicitis: sonographic findings and clinical management implications. Ultrasound Q 2011; 27:71-9.
  18. Kunz PL, Mojtahed A, Fisher GA, Ford JM, Chang DT, Balise RR, Bangs CD, Cherry AM, Pai RK. HER2 Expression in gastric and gastroesophageal junction adenocarcinoma in a US population: Clinicopathologic analysis with proposed approach to HER2 Assessment. Appl Immunohistochem Mol Morphol 2011; 20: 13-24.
  19. Pai RK, Mojtahed A, Rouse RV, Soetikno RM, Kaltenbach T, Ma L, Arber DA, Plesec TP, Goldblum JR, Pai RK. Histologic and molecular analysis of colonic perineurial-like proliferations in serrated polyps: Sessile serrated adenomas frequently display perineurial-like stromal proliferations. Am J Surg Pathol 2011; 35: 1373-3780.
  20. Deshpande N, Lutz AM, Ren Y, Foygel K, Tian L, Pai R, Pasricha PJ, Willman JK.. Quantification and Monitoring of Inflammation in Murine Inflammatory Bowel Disease using Targeted Contrast-enhanced Ultrasound Imaging. Radiology 2011; 262: 172-180.
  21. Dudley J, Pai RK, Pasricha PJ, Bhutte A. Computational repositioning of the anticonvulsant topiramate in inflammatory bowel disease. Science Translational Medicine 2011; 3: 1-6.
  22. Qadan M, Visser B, Kim J, Pai R, Triadafilopoulos G. Abdominal Mass, Anemia, Diabetes Mellitus, and Necrolytic Migratory Erythema. Dig Dis Sci 2011. [Epub ahead of print]
  23. Pai RK, Jayachandran P, Koong AC, Chang DT, Kwok S, Arber DA, Balise RR, Tubbs RR, Shadrach B, Pai RK. BRAF-mutated, microsatellite stable adenocarcinoma of the proximal colon: An aggressive adenocarcinoma with poor survival, mucinous differentiation, and adverse morphologic features. Am J Surg Pathol 2012; 36: 744-752.
  24. Le-Carlson M, Triadafilopoulos G, Pai RK, Kerner JA. An Evolving Case of Concurrent Eosinophilic Esophagitis and Eosinophilic Gastroenteritis. Dig Dis Sci 2012 [Epub ahead of print].
  25. Tun MT, Pai RK, Kwok S, Dong A, Gupta A, Visser BC, Norton JA, Poultsides GA, Banerjee S, Van Dam J, Chen AM, Friedland S, Scott BA, Verma R, Lowe AW, Park WG. Diagnostic accuracy of cyst fluid amphiregulin in pancreatic cysts. BMC Gastroenterol 2012;12(1):15.
  26. Chang DT, Pai RK, Rybicki L, Dimaio M, Limaye M, Jayachandran P, Koong A, Kunz, P, Fisher GA, Ford JM, Welton M, Shelton A, Ma L, Arber D, Pai RK. Clinicopathologic and molecular features of sporadic early-onset colorectal adenocarcinoma: an adenocarcinoma with frequent signet ring cell differentiation, rectal and sigmoid involvement, and adverse morphologic features. Mod Pathol 2012. [Epub ahead of print]
  27. Poultsides GA, Huang LC, Chen Y, Visser BC, Pai RK, Jeffrey RB, Park WG, Chen AM, Kunz PL, Fisher GA, Norton JA. Pancreatic neuroendocrine tumors: radiographic calcifications correlate with grade and metastasis. Ann Surg Oncol 2012 [Epub ahead of print]
  28. Fujiwara M, Yano H, Kwok S, Pai RK. Arginase-1 is a more sensitive marker of hepatic differentiation than HepPar-1 and glypican-3 in fine needle aspiration biopsies. Cancer Cytopathol 2012. [Epub ahead of print]
  29. Jayachandran P, Pai RK, Quon A, Graves E, Krakow TE, La T, Loo BW Jr, Koong AC, Chang DT. Postchemoradiotherapy Positron Emission Tomography Predicts Pathologic Response and Survival in Patients with Esophageal Cancer. Int J Radiat Oncol Biol Phys. 2012 [Epub ahead of print].
  30. Dimaio M, Kwok S, Montgomery K, Lowe AW, Pai RK. Immunohistochemical Panel for Distinguishing Esophageal Adenocarcinoma from Squamous Cell Carcinoma: A Combination of p63, Cytokeratin 5/6, MUC5AC, and AGR2 Allows Optimal Subtyping. Hum Pathol 2012. [In Press]