Non-small-cell lung carcinoma (NSCLC) is any type of epithelial lung cancer other than small-cell lung carcinoma (SCLC). NSCLC accounts for about 85% of all lung cancers. As a class, NSCLCs are relatively insensitive to chemotherapy, compared to small-cell carcinoma. When possible, they are primarily treated by surgical resection with curative intent, although chemotherapy has been used increasingly both preoperatively (neoadjuvant chemotherapy) and postoperatively (adjuvant chemotherapy). Types
The most common types of NSCLC are squamous-cell carcinoma, large-cell carcinoma, and adenocarcinoma, but several other types occur less frequently. A few of the less common types are pleomorphic, carcinoid tumor, salivary gland carcinoma, and unclassified carcinoma. All types can occur in unusual histologic variants and as mixed cell-type combinations. Nonsquamous-cell carcinoma almost occupies the half of NSCLC. In the tissue classification, the central type contains about one-ninth.Sometimes, the phrase "not otherwise specified" (NOS) is used generically, usually when a more specific diagnosis cannot be made. This is most often the case when a pathologist examines a small number of malignant cells or tissue in a cytology or biopsy specimen.Lung cancer in people who have never smoked is almost universally NSCLC, with a sizeable majority being adenocarcinoma.On relatively rare occasions, malignant lung tumors are found to contain components of both SCLC and NSCLC. In these cases, the tumors are classified as combined small-cell lung carcinoma (c-SCLC), and are (usually) treated as "pure" SCLC. Lung adenocarcinoma
Adenocarcinoma of the lung is currently the most common type of lung cancer in "never smokers" (lifelong nonsmokers). Adenocarcinomas account for about 40% of lung cancers.
Historically, adenocarcinoma was more often seen peripherally in the lungs than SCLC and squamous-cell lung cancer, both of which tended to be more often centrally located. Recent studies, though, suggest that the "ratio of centrally to peripherally occurring" lesions may be converging toward unity for both adenocarcinoma and squamous-cell carcinoma. Squamous-cell lung carcinoma
Squamous-cell carcinoma (SCC) of the lung is more common in men than in women. It is closely correlated with a history of tobacco smoking, more so than most other types of lung cancer. According to the Nurses Health Study, the relative risk of SCC is around 5.5, both among those with a previous duration of smoking of 1 to 20 years, and those with 20 to 30 years, compared to "never smokers" (lifelong nonsmokers). The relative risk increases to about 16 with a previous smoking duration of 30 to 40 years, and roughly 22 with more than 40 years. Large-cell lung carcinoma
Large-cell lung carcinoma (LCLC) is a heterogeneous group of undifferentiated malignant neoplasms originating from transformed epithelial cells in the lung. LCLCs have typically comprised around 10% of all NSCLC in the past, although newer diagnostic techniques seem to be reducing the incidence of diagnosis of "classic" LCLC in favor of more poorly differentiated SCCs and adenocarcinomas. LCLC is, in effect, a "diagnosis of exclusion", in that the tumor cells lack light microscopic characteristics that would classify the neoplasm as a small-cell carcinoma, squamous-cell carcinoma, adenocarcinoma, or other more specific histologic type of lung cancer.