Mesenchymal tumors of the lung: diagnostic pathology, molecular pathogenesis, and identified biomarkers

Lung cancers are primarily composed of epithelial tumors such as carcinomas. As mesenchymal tumors in the lung are very rare, they have garnered little attention. The 2015 World Health Organization (WHO) classification of lung tumors has undergone revision, not only for carcinomas but also for mesenchymal tumors (1,2); for example, PEComatous tumors, myoepithelial tumors, and pulmonary myxoid sarcomas with EWSR1-CREB1 translocation have been adopted as new disease entities (1,2). To date, no review articles have comprehensively summarized what is known about pulmonary mesenchymal tumors in accordance with the latest WHO classification. We present current data about these tumors (except for pediatric tumors), with a special emphasis on their diagnostic pathology, molecular pathogenesis, and identified biomarkers, in line with the 2015 WHO classification. We also describe recently recognized pulmonary mesenchymal tumors that have not yet been included in the WHO classification (Table 1)