Thursday, June 27, 2013

LUNG CANCER-PART III

     Types of lung cancer
Lung cancer is caused by the uncontrolled growth (proliferation) of abnormal cells inside the lung. There are two main forms of the disease, non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) (Barzi and Pennell, 2010).
SCLC constitutes approximately 16% of all primary lung cancers, accounting for more than 35,000 cases per year (Jemal et al., 2009).  NSCLC is the most common form of the disease, accounting for approximately 85% of all cases.  NSCLC can be further divided into adenocarcinoma, squamous cell carcinoma and large cell carcinoma. This different NSCLC types are present in different parts of the lung as shown in the figure below. SCLC is distinguished from NSCLC by its rapid growth rate, early dissemination to regional lymph nodes and distant sites, and its sensitivity to chemotherapy and radiotherapy (Masters et al., 2005). SCLC is almost exclusively caused by smoking. Two-thirds of SCLC patients present with extensive stage disease (ES-SCLC) due to a tendency to metastasize early to distant sites, including the brain, bones, liver, and adrenals (Ettinger and Johnson, 2005).


SCLC showed the smallest values for nuclear size (mean core score of 1.18) and DNA content (DNA index mean of 2.08c) being highly significantly different from adenocarcinoma (1.95/3.10c), large cell lung carcinoma (2.00/3.26c) and squamous cell carcinoma (2.20/3.42c).  In NSCLC in general and adenocarcinoma in particular, the core size variability correlated significantly with grading and survival (Petersen, 2009).