Lung Cancer - Pathology

Pathology
There are benign and malignant tumors of the lung. Malignant or
cancerous lung tumors are classified into two major categories: small
cell (20%) and non-small cell carcinomas (80%). The non-small cell
tumors are subdivided into three types: squamous cell (30%),
adenocarcinomas (35%), and large cell carcinomas (15%). Although each
of the four tumors have fairly distinctive clinical and radiologic
characteristics, determination of the exact pathologic type requires
biopsy of the primary lung tumor or the peripheral organs involved by
metastatic spread. Occasionally, special immunohistochemical stains
may be required to identify specific cell types.
Small cell carcinoma is considered of neuroendocrine in origin. In
terms of treatment these group of tumors are managed mainly with
chemotherapy and radiation therapy, rarely surgery is of any benefit.
Conversely, non-small cell carcinomas are treated with surgery in their
earlier stages.
Squamous cell carcinomas are often centrally located, either in the
main bronchus of the proximal portion of the lobar bronchus, frequently
leading to partial or complete bronchial obstruction. Sputum cytology
examinations are often positive, and the tumor can be visualized at
bronchoscopy.
Adenocarcinomas of the lung are commonly peripheral in location,
presenting as a solitary nodule or mass. Women present more often with
peripheral adenocarcinoma than do men. Sputum cytology is often
negative and bronchoscopy frequently fails to demonstrate the tumor.
Bronchoalveolar or alveolar cell carcinomas which comprise 5% of
malignant lung tumors are considered to be a subgroup of the
adenocarcinomas. The tumor cells arise in the terminal portion of the
bronchial tree and alveoli and grow along the alveolar walls and airway
without disturbing the alveolar architecture. If the tumor is
unifocal, small, and non-mucinous, prognosis after surgical removal is
excellent.
Large cell carcinomas present frequently as a large, lobulated
parenchymal mass that is often cavitated. Hemoptysis (blood in the
sputum) is common, and poor prognosis is frequently associated to this
tumor type.