Ung thư phổi
1) Four main histological subtypes of lung cancer are regularly distinguished by tumor morphology under the light microscope. Squamous and small cell tumors account for approximately 30 percent and 19 percent of all lung cancers, respectively. These cancers are believed to derive mainly from epithelial cells that line the larger airways. Adenocarcinomas comprise 30 percent of all lung cancers, and these tumors are believed to derive from epithelial cells that line the peripheral small airways. Finally, 10 percent of lung tumors are classified as "large cell", a poorly differentiated subtype usually diagnosed by exclusion of the other 3 types of lung cancer. Like adenocarcinomas, large cell tumors are preferentially located in the periphery of the lung.
2) Patients with non-small cell lung tumors (squamous, adenocarcinomas, and large cell) are treated differently from those with small cell tumors. The pathological distinction between small cell lung cancer and non-small cell lung cancer is therefore very important. There is a relative consensus among pathologists on the diagnosis of small cell cancer. These tumors progress along a typical clinical course that is characterized by an excellent initial response to chemotherapy and is often associated with several months of complete regression. This short-term regression, however, is followed by recurrence, development of chemo-resistance, and finally death caused by systemic dissemination. In contrast, the morphological subtyping of non-small cell lung cancer is more difficult and far less reliable in predicting patient outcome. Approximately 50 percent of patients die from metastatic disease even after complete surgical removal of the primary tumor. The initial tumor pathologic diagnosis is based on small bronchoscopic biopsy specimens and may change when surgically removed specimens are reexamined. Lung tumor heterogeneity is well documented and is reflected in the morphological classification of mixed tumors such as adenosquamous carcinoma or combined small cell lung cancer containing both small cell and non-small cell components.
Proc. Nat. Acad. Sci. 2001 98:13784
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