The differential diagnosis between pleural sarcomatoid mesothelioma and spindle cell/pleomorphic (sarcomatoid) carcinomas of the lung: Evidence-Based guidelines from the International Mesothelioma Panel and the MESOPATH National Reference Center

Publication date: Available online 4 August 2017
Source:Human Pathology
Author(s): Alberto M. Marchevsky, Nolwenn LeStang, Kenzo Hiroshima, Giuseppe Pelosi, Richard Attanoos, Andrew Churg, Lucien Chirieac, Sanja Dacic, Aliya Husain, Andras Khoor, Sonja Klebe, Silvie Lantuejoul, Victor Roggli, Jean-Michel Vignaud, Birgit Weynand, Jennifer Sauter, Douglas Henderson, Kazuki Nabeshima, Francoise Galateau-Salle
Immunohistochemistry is used to distinguish sarcomatoid malignant mesotheliomas (SMM) from spindle cell and pleomorphic carcinomas (SPC) but there are no guidelines on how to interpret cases that show overlapping or equivocal immunohistochemical findings. A systematic literature review of the immunophenotype of these lesions was performed and the experience with 587 SMM and 46 SPC at MESOPATH was collected. Data were analyzed with Comprehensive Meta-Analysis 2.0 software (Biostast, Englewood N.J.). There were insufficient data to evaluate the differential diagnosis between SPC and localized SMM or peritoneal SMM. Meta-analysis showed considerable overlap in the immunophenotype of these neoplasms and significant data heterogeneity amongst many of the results. Survival data from MESOPATH patients showed no significant differences in overall survival between SMM and SPC patients. Best-available evidence was used to formulate several evidence-based guidelines for the differential diagnosis between pleural SMM and SPC. These guidelines emphasize the need to correlate the histopathological findings with clinical and imaging information. Diffuse SMM can be diagnosed with certainty in the presence of malignant spindle cell pleural lesions showing immunoreactivity for cytokeratin and mesothelial markers and negative staining for epithelial markers. Criteria for the interpretation of various other combinations of immunoreactivity for cytokeratin, mesothelial and/or epithelial markers are proposed. Localized sarcomatoid mesotheliomas can only be diagnosed in the presence of spindle cell malignancies that exhibit immunoreactivity for cytokeratin and mesothelial markers and negative immunoreactivity for epithelial lesions, in patients that show no multifocal or diffuse pleural spread and no evidence for extrapleural lesions.



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