An Update on the Classification of Lung and Pleural Tumors

The World Health Organization (WHO) recently published new guidelines for the diagnosis and classification of lung and pleural tumors. This review provides a concise overview of the key updates, including discussions of histologic features and recommended terminology for small diagnostic lung samples, the revised grading system for lung adenocarcinoma with inclusion of complex glandular and filigree micropapillary patterns, and molecular features of large cell neuroendocrine carcinoma. Additionally, rare neoplasms such as bronchiolar adenoma/ciliated muconodular papillary tumor, SMARCA4-deficient undifferentiated thoracic tumor, and primary pulmonary hyalinizing clear cell carcinoma are described in terms of their diagnostic approaches and molecular features. This review also includes discussion of the diagnostic algorithm for malignant epithelioid mesothelioma.