Non–Small Cell Lung Cancer

Excerpt

Lung cancer is a diagnosis that approximately 230,000 United States citizens will receive annually. Deaths are estimated at 135,000 patients per year. Lung cancer deaths have become more numerous than the deaths from prostate, breast, brain, and colorectal cancer combined. It has now become the most common cause of cancer deaths in men and the second most common in women. However, this statistic is now declining largely due to anti-smoking campaigns and decreased tobacco use in the United States.

The foundation of lung tumor classification follows the 2015 World Health Organization (WHO) classification of lung tumors. This classification system relies on immunohistochemistry and light microscopy in order to better guide treatment and determine a prognostic course. Non-small cell lung cancer (NSCLC) is a term that includes a variety of different lung cancers, most notably adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. Adenocarcinoma is the most common type of lung cancer in this category and includes one-half of all lung cancer cases. Squamous cell carcinoma is another type of NSCLC that had been the most frequently diagnosed lung cancer before this time. Squamous cell carcinoma (SCC) usually originates at the origin of the tracheobronchial tree, but more cases are now diagnosed in the periphery of the lung.

Large cell carcinoma is a subset of NSCLC that is a diagnosis of exclusion. It is poorly differentiated and cannot be further classified by immunohistochemistry (IHC) or electron microscopy. However, 90% of cases will show squamous, glandular, or neuroendocrine differentiation. NSCLC also includes other subsets of lung cancer, with both heterogeneous categories and broad terminology. These include adenosquamous carcinoma, sarcomatoid carcinoma, and non-small cell neuroendocrine tumors.