IPLab:Lab 7:Bronchogenic Carcinoma
This 55-year-old white male had a long history of emphysema and a 60-70 pack-year smoking history. He was in his usual state of health until about one month before admission, at which time he developed increasing dyspnea on exertion. At the same time, his sputum increased from two tablespoons to half a cup of yellow blood-streaked sputum a day. Chest x-ray showed a right hilar mass. Sputum cytology revealed abnormal cells that were "positive for malignancy." He later developed pneumonia and fever. The patient expired soon thereafter.
Significant findings included advanced carcinoma of the right main stem bronchus with extension across the carina to produce obstruction of the left main stem bronchus. There was left lower lobe pneumonia and left upper lobe atelectasis. Extensive metastases were present in regional lymph nodes as well as the pericardium, left atrium, and right kidney.
This is a gross photograph of bronchogenic carcinoma. The large tumor mass can be seen adjacent to the bronchus (1). Note that the epithelial surface of the bronchus is rough and irregular (2). The first branch off the right main stem bronchus is partially occluded by the thickened mucosa and submucosa (3).
- What are the four main histologic classifications of bronchiogenic carcinoma and what are their relative frequencies?
Squamous cell carcinoma, and adenocarcinoma occur at approximately equal frequency, 25 to 40% each; small cell carcinoma, 20 to 25%; and large cell carcinoma, 10 to 15%.
- There is a positive relationship between tobacco smoking and lung cancer. Compared with nonsmokers, cigarette smokers have a ten-fold greater risk of developing lung cancer, and heavy smokers (more than 40 cigarettes per day for several years) have at least a 20-fold greater risk. Eighty per cent of lung cancers occur in smokers.
- Industrial hazards (uranium, asbestos, etc.).
- Air pollution (radon).
- Genetic factors. Occasional familial clustering has been observed suggesting a genetic component to lung cancer. Dominant oncogenes (c-myc in small cell carcinoma & K-ras in adenocarcinomas) and loss or inactivation of recessive tumor suppressor genes (p53 & retinoblastoma) have been reported in lung cancer.
- Scarring. Some lung cancers arise in the area of old scars and are termed scar carcinomas.
- Antidiuretic hormone (ADH), inducing hyponatremia due to inappropriate ADH secretion;
- adrenocorticotropic hormone (ACTH), producing Cushing’s syndrome;
- parathormone, parathyroid hormone-related peptide, prostaglandin E, and some cytokines, all implicated in the hypercalcemia often seen with lung cancer;
- calcitonin, causing hypocalcemia;
- gonadotropins, causing gynecomastia; and
- serotonin, associated with the carcinoid syndrome. The incidence of clinically significant syndromes related to these factors ranges from 1 to 10% of all lung cancer patients. Any one of the histologic types of tumors may occasionally produce any one of the hormones, but tumors producing ACTH and ADH are predominantly small cell carcinomas and those producing hypercalcemia are mostly squamous cell tumors.
The clinical course is somewhat variable but in general the prognosis is poor with a 5 year survival of approximately 9%.
Pulmonary emphysema is a condition in which the air spaces distal to the terminal bronchioles are permanently increased in size due to either destruction of the wall or alveolar dilatation.
A pack-year denotes smoking one pack of cigarettes per day for one year.
In alcoholics, aspiration pneumonia is common--bacteria enter the lung via aspiration of gastric contents.
Atelectasis is the collapse of an airway and lung, regardless of the cause, resulting in reduced or absent gas exchange.
Hypercalcemia is the state of having increased levels of calcium in the blood.