Highlights of the 14th international mesothelioma interest group meeting: Pathologic separation of benign from malignant mesothelial proliferations and histologic/molecular analysis of malignant mesothelioma subtypes

Lung Cancer. 2018 Oct;124:95-101. doi: 10.1016/j.lungcan.2018.07.041. Epub 2018 Jul 30.


Objectives: The separation of benign from malignant mesothelial proliferations and exact subclassification of mesothelioma subtypes is crucial to determining patient care and prognosis but morphologically can be very difficult.

Methods: This session of the 2018 IMIG meeting addressed these problems.

Results: A new immunohistochemical marker, methylthioadenosine phosphorylase, was shown to correlate well with CDKN2A FISH and is cheaper and faster to run. A 117 gene expression panel also provided good separation on both tissue biopsy and cytology samples. Review of a series of mesotheliomas thought to be biphasic produced only a moderate level of agreement among expert pathologists with some cases being classified as purely epithelioid or sarcomatoid; these classifications had prognostic significance. The entity called transitional mesothelioma was found to behave exactly like sarcomatoid mesothelioma. RNA-seq analysis of a large series of mesotheliomas from a public database showed that, genetically, the morphologic breakdown into epithelioid, sarcomatoid, or biphasic mesotheliomas is artificial because there is a continuous spectrum of genomic changes. There are now criteria for the diagnosis of mesothelioma in situ and this is potentially important, since such cases might be curable.

Conclusions: This session documented new morphological and molecular approaches to separating benign from malignant mesothelial proliferations and to subclassifying malignant mesoteheliomas in clinical relevant ways.

Keywords: BAP1; CDKN2A FISH; Malignant mesothelioma; Methylthioadenosine phosphorylase; Reactive mesothelial proliferations.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers, Tumor / metabolism*
  • Cell Proliferation
  • Congresses as Topic
  • Consensus
  • Cyclin-Dependent Kinase Inhibitor p16 / genetics
  • Cyclin-Dependent Kinase Inhibitor p16 / metabolism*
  • Diagnosis, Differential
  • Epithelium / metabolism
  • Epithelium / pathology*
  • Expert Testimony
  • Group Processes
  • Humans
  • Immunohistochemistry
  • In Situ Hybridization, Fluorescence
  • International Cooperation
  • Lung Neoplasms / diagnosis*
  • Lung Neoplasms / pathology
  • Mesothelioma / diagnosis*
  • Mesothelioma / pathology
  • Mesothelioma, Malignant
  • Pathology, Molecular
  • Phenotype
  • Public Opinion
  • Solitary Fibrous Tumor, Pleural / classification
  • Solitary Fibrous Tumor, Pleural / diagnosis*
  • Solitary Fibrous Tumor, Pleural / pathology


  • Biomarkers, Tumor
  • CDKN2A protein, human
  • Cyclin-Dependent Kinase Inhibitor p16