This text consists of neoplastic and non-neoplastic lung pathology. It discusses frequently encountered issues and diagnostic problems using a Q&A format and case presentations. Emphasis is placed on differentiating one from another based on the histopathological features, ancillary tests including immunohistochemical and molecular analyses, and clinical and radiologic correlation. In particular, clinical-radiologic-pathologic correlation is emphasized in the diagnosis of interstitial lung disease (ILD). This text addresses the issues and diagnostic criteria in segregating a reactive process from adenocarcinoma, poorly differentiated adenocarcinoma from poorly differentiated squamous cell carcinoma, small cell carcinoma from other types of neuroendocrine tumors, large cell carcinoma from large cell neuroendocrine carcinoma, spindle cell/sarcomatoid carcinoma from sarcomatoid mesothelioma, and carcinoma from epithelioid mesothelioma in small biopsy specimens.