Aliya Noor Husain, Thomas V. Colby, Nelson G. Ordóñez, Timothy Craig Allen, Richard Luther Attanoos, Mary Beth Beasley, Kelly Jo Butnor, Lucian R. Chirieac, Andrew M. Churg, Sanja Dacic, Françoise Galateau-Sallé, Allen Gibbs, Allen M. Gown, Thomas Krausz, Leslie Anne Litzky, Alberto Marchevsky, Andrew G. Nicholson, Victor Louis Roggli, Anupama K. Sharma, William D. Travis, Ann E. Walts, and Mark R. Wick (2017) Guidelines for Pathologic Diagnosis of Malignant Mesothelioma: 2017 Update of the Consensus Statement From the International Mesothelioma Interest Group. Archives of Pathology & Laboratory Medicine In-Press.

https://doi.org/10.5858/arpa.2017-0124-RA

Early Online Release

Guidelines for Pathologic Diagnosis of Malignant Mesothelioma: 2017 Update of the Consensus Statement From the International Mesothelioma Interest Group

Aliya Noor Husain, MD; Thomas V. Colby, MD; Nelson G. Ordóñez, MD; Timothy Craig Allen, MD, JD; Richard Luther Attanoos, MBBS, MD, FRCPath; Mary Beth Beasley, MD; Kelly Jo Butnor, MD; Lucian R. Chirieac, MD; Andrew M. Churg, MD; Sanja Dacic, MD, PhD;Françoise Galateau-Sallé, MD; Allen Gibbs, MD; Allen M. Gown, MD; Thomas Krausz, MD; Leslie Anne Litzky, MD; Alberto Marchevsky, MD; Andrew G. Nicholson, DM; Victor Louis Roggli, MD; Anupama K. Sharma, MD; William D. Travis, MD; Ann E. Walts, MD; Mark R. Wick, MD

From the Department of Pathology, University of Chicago Medical Center, Chicago, Illinois (Drs Husain and Krausz); the Department of Laboratory Medicine and Pathology, Mayo Clinic, Scottsdale, Arizona (Dr Colby, emeritus); the Department of Pathology, University of Texas, MD Anderson Cancer Center, Houston (Dr Ordóñez); the Department of Pathology, University of Texas Medical Branch, Galveston (Dr Allen); the Department of Cellular Pathology, University Hospital of Wales and Cardiff University, Cardiff, South Glamorgan, Wales (Dr Attanoos); the Department of Pathology, Mount Sinai Medical Center, New York, New York (Dr Beasley); the Department of Pathology, University of Vermont College of Medicine, Burlington (Dr Butnor); the Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts (Dr Chirieac); the Department of Pathology, Vancouver General Hospital, Vancouver, British Columbia, Canada (Dr Churg); the Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania (Dr Dacic); Centre National Référent MESOPATH Departement de Biopathologie, Lyon Cedex, France (Dr Galateau-Sallé); the Department of Pathology, University Hospital of Wales, Penarth, South Glamorgan, Wales (Dr Gibbs); the Department of Pathology, PhenoPath Laboratories, Seattle, Washington (Dr Gown); the Department of Pathology & Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia, (Dr Litzky); the Department of Pathology & Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, California (Drs Marchevsky and Walts); the Department of Histopathology, Royal Brompton & Harefield National Health Service Foundation Trust and the National Heart and Lung Institute, Imperial College, Chelsea, London, England (Dr Nicholson); the Department of Pathology, Duke University Medical Center, Durham, North Carolina (Dr Roggli); the Department of Pathology, University of Pittsburgh, and the VA Pittsburgh Healthcare System, Pittsburgh, Pennsylvania (Dr Sharma); the Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York (Dr Travis); and the Department of Pathology, University of Virginia Medical Center, Charlottesville (Dr Wick).

Reprints: Aliya N. Husain, MD, Department of Pathology, MC6101, University of Chicago Medical Center, 5841 S Maryland Ave, Room S-627, Chicago, IL 60637 (email: aliya.husain@uchospitals.edu).

Context.— Malignant mesothelioma (MM) is an uncommon tumor that can be difficult to diagnose.

Objective.— To provide updated, practical guidelines for the pathologic diagnosis of MM.

Data Sources.— Pathologists involved in the International Mesothelioma Interest Group and others with an interest and expertise in the field contributed to this update. Reference material included up-to-date, peer-reviewed publications and textbooks.

Conclusions.— There was discussion and consensus opinion regarding guidelines for (1) distinguishing benign from malignant mesothelial proliferations (both epithelioid and spindle cell lesions), (2) cytologic diagnosis of MM, (3) recognition of the key histologic features of pleural and peritoneal MM, (4) use of histochemical and immunohistochemical stains in the diagnosis and differential diagnosis of MM, (5) differentiating epithelioid MM from various carcinomas (lung, breast, ovarian, and colonic adenocarcinomas, and squamous cell and renal cell carcinomas), (6) diagnosis of sarcomatoid MM, (7) use of molecular markers in the diagnosis of MM, (8) electron microscopy in the diagnosis of MM, and (9) some caveats and pitfalls in the diagnosis of MM. Immunohistochemical panels are integral to the diagnosis of MM, but the exact makeup of panels employed is dependent on the differential diagnosis and on the antibodies available in a given laboratory. Depending on the morphology, immunohistochemical panels should contain both positive and negative markers for mesothelial differentiation and for lesions considered in the differential diagnosis. Immunohistochemical markers should have either sensitivity or specificity greater than 80% for the lesions in question. Interpretation of positivity generally should take into account the localization of the stain (eg, nuclear versus cytoplasmic) and the percentage of cells staining (>10% is suggested for cytoplasmic and membranous markers). Selected molecular markers are now being used to distinguish benign from malignant mesothelial proliferations. These guidelines are meant to be a practical diagnostic reference for the pathologist; however, some new pathologic predictors of prognosis and response to therapy are also included.