Download Pathology and the Lung Cancer Patient

Pathology and the Lung Cancer Patient
Angela Konrad, DO
Pathologist
Cancer Liaison Physician, Cancer Committee
Today lung cancer remains the most frequent cause of cancer death in the United States. Tobacco
smoking is the major cause of lung cancer. In male smokers, the risk of developing lung cancer is 8-15
times higher than in nonsmokers. In female smokers, the risk is 3-10 times higher versus non-smokers.
The majority of lung cancers are carcinomas derived from the bronchial epithelium. There are four main
types of lung cancer categorized by their histopathologic appearance. These include small cell
carcinoma, adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. All of these types
share the risk factor of smoking. Small cell carcinomas and squamous cell carcinomas have the
strongest association with smoking. In the past, two broad categories were used for classification, small
cell carcinoma and non-small cell carcinoma (NSCLC). The non-small cell carcinomas include
adenocarcinoma, squamous cell carcinoma, and large cell carcinoma.
Small cell carcinoma shows neuroendocrine differentiation. The tumor consists of small cells with little
cytoplasm, "salt and pepper" type chromatin in the nucleus, abundant necrosis, and numerous mitoses.
Small cell carcinomas have an aggressive course and are the most aggressive lung tumors. They are
known to have widespread metastases and are incurable by surgery. These tumors only show a
temporary response to chemotherapy and radiotherapy treatments.
Adenocarcinoma is a malignant tumor with areas of gland formation and mucin production. There are
subtypes based on the appearance of the tumor which include: acinar, papillary, bronchioloalveolar,
and solid patterns. However, the majority of tumors shows a mixture of these patterns and therefore
falls into the mixed category. Adenocarcinomas are frequently found in the periphery of the lung.
According to the National Cancer Database Data, for NSCLC, adenocarcinoma is the most common type,
comprising 37%. Here at Mercy North Iowa, adenocarcinoma is the most common NSCLC at 44%.
Adenocarcinoma is the most common type of lung cancer in women and nonsmokers. However, these
tumors still show a strong association with smoking (greater than 75% occur in smokers).
Squamous cell carcinoma displays evidence of keratin formation. This can be in the form of keratin
pearls or intercellular bridges. This tumor typically arises in the center of the lung. Survival rates for
squamous cell carcinoma are better than for adenocarcinoma.
Large cell carcinoma is an undifferentiated tumor that lacks squamous, glandular, or small cell
differentiation. This is a diagnosis of exclusion.
The stage of cancer is a major factor in determining prognosis. Lung cancer is often diagnosed at an
advanced stage. The overall five year survival is approximately 15%. Clinical and pathologic staging is
necessary to determine the appropriate treatment for patients. Staging also helps to evaluate the
results of treatment and cancer research. Several cancer staging systems are used. One of the more
common is the tumor node metastasis (TNM) system. The pathologic stage is determined by
anatomically and histologically examining tumor. At resection, the tumor size is determined and the
bounds of the tumor are assessed. Based on these data, the primary tumor will then be assigned a p (T)
score. The involvement of regional lymph nodes is assessed and the tumor is given a p (N) score. The
presence or absence of distant metastases is also determined and the tumor is given a p (M) score.
Based on the TNM score, the tumor is then categorized into an anatomic stage/prognostic group. These
are classified from stage I through stage IV with the higher stage having more severe disease. According
to the National Cancer Database, most NSCLC are diagnosed at stage III (24%) or stage IV (36%). At
Mercy North Iowa, 23% of all NSCLC are diagnosed at stage III and 39% are diagnosed at stage IV.