This document provides information on primary pulmonary neoplasms (lung cancer). It discusses the epidemiology and causes of lung cancer, including the major risk factor of cigarette smoking. It then covers the histologic classification of lung cancers, distinguishing between non-small cell lung carcinoma (NSCLC) and small cell lung carcinoma. Within NSCLC, it describes the characteristics and radiologic manifestations of the main subtypes: squamous cell carcinoma, adenocarcinoma, and other rare types. Key precursor lesions like atypical adenomatous hyperplasia and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia are also summarized.