Classification Lung cancer is a large and exceptionally heterogeneous family of malignancies. Over 50 different histological variants are explicitly recognized within the 2004 revision of the World Health Organization (WHO) typing system ("WHO-2004"), currently the most widely used lung cancer classification scheme. Many of these entities are rare, recently described, and poorly understood. However, since different forms of malignant tumors generally exhibit diverse genetic, biological, and clinical properties, including response to treatment, accurate classification of lung cancer cases are critical to assuring that patients with lung cancer receive optimum management. Approximately 98% of lung cancers are carcinoma, a term for malignant neoplasms derived from cells of epithelial lineage, and/or that exhibit cytological or tissue architectural features characteristically found in epithelial cells. Under WHO-2004, lung carcinomas are divided into 8 major taxa: * Squamous cell carcinoma * Small cell carcinoma * Adenocarcinoma * Large cell carcinoma * Adenosquamous carcinoma *<unk>  carcinoma * Carcinoid tumor * Salivary gland-like carcinoma<unk>  carcinomas are unique among lung carcinomas in that, although they are considered carcinomas, they contain cytological and tissue architectural features that are usually characteristic of sarcoma.
Sarcomatoid carcinoma of the lung
Epithelial-myoepithelial carcinoma of the lung
Giant-cell carcinoma of the lung
Pulmonary sclerosing pneumocytoma
Mucinous cystadenocarcinoma of the lung
Adenocarcinoma of the lung
Salivary gland–like carcinoma of the lung
Adenosquamous lung carcinoma