Lung cancers are now considered a large and extremely heterogeneous family of neoplasms that feature widely varying genetic, biological, and clinical characteristics. About 50 different lung cancer variants are recognized under the 2004 revision of the World Health Organization ("WHO-2004") histological typing system, the most widely recognized and used lung cancer classification scheme. Recent studies have shown beyond doubt that the old classification paradigm of "small<unk>  carcinoma vs. non-small<unk>  carcinoma" is now obsolete, and that the correct "subclassification" of lung cancer cases is necessary to assure that patients receive optimum management. More than 99% of primary lung cancers are carcinoma, which are tumors composed of<unk> s that originate from embryonic ectoderm or endoderm, or that feature epithelial characteristics or differentiation. Eight major groups of lung carcinomas are recognized in WHO-2004: ::*Squamous<unk>  lung carcinoma ::*Small<unk>  lung carcinoma ::*Adenocarcinoma of the lung ::*Large<unk>  lung carcinoma ::*Adenosquamous carcinoma ::*Sarcomatoid carcinoma ::*Carcinoid tumor ::*Salivary gland-like carcinoma of the lung LCLC-RP are considered variants of large<unk>  carcinoma.
Large-cell lung carcinoma with rhabdoid phenotype
Epithelial-myoepithelial carcinoma of the lung
Salivary gland–like carcinoma of the lung
Mucinous cystadenocarcinoma of the lung
Basaloid large cell carcinoma of the lung
Large cell neuroendocrine carcinoma of the lung
Plexiform angiomyxoid myofibroblastic tumor
Atypical pulmonary carcinoid tumour