Classification<unk>  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<unk>  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<unk>  cancer cases are critical to assuring that patients with<unk>  cancer receive optimum management. Under WHO-2004,<unk>  carcinomas are divided into 8 major taxa: * Squamous cell carcinoma * Small cell carcinoma * Adenocarcinoma * Large cell carcinoma * Adenosquamous carcinoma * Sarcomatoid carcinoma * Carcinoid tumor *<unk><unk> -like carcinoma
Salivary gland–like carcinoma of the lung
Epithelial-myoepithelial carcinoma of the lung
Atypical pulmonary carcinoid tumour
Mucinous cystadenocarcinoma of the lung
Large cell neuroendocrine carcinoma of the lung
Combined small-cell lung carcinoma
Pulmonary neuroendocrine tumor
Giant-cell carcinoma of the lung