IPLab:Lab 12:Thoracic Mesothelioma
This 61-year-old white male had a known history of asbestos exposure when in his twenties he had worked on a construction crew installing insulation in public buildings. The patient had a 40 pack-yearA pack-year denotes smoking one pack of cigarettes per day for one year. history of smoking and a history of coronary artery disease requiring a coronary artery bypass graft ten years prior to his final admission. Two years prior to this admission, an open lung biopsy showed the patient to have a thoracic mesothelioma for which he was treated with radiation therapy. The patient was then placed on steroidal and nonsteroidal pain medications and a nerve block was performed to help alleviate the discomfort. On final admission, the patient complained of shortness of breathShortness of breath is a common clinical manifestation of heart failure., orthopnea, and pedal edema. Physical examination revealed mild respiratory distress on nasal oxygen, a dull left hemothorax, and right basal bronchial breath sounds with scattered rales. Chest x-ray demonstrated a left hemothorax opacity, small right pleural effusionsPleural effusion is the presence of fluid in the pleural space. Increased hydrostatic pressure in the pulmonary vasculature, as seen in heart failure, is one cause of pleural effusion., and pleural plaques. The patient subsequently developed atrial fibrillation and immediately prior to his death he suffered a stroke.
Tumor plaque covered 100% of the left lung, 50% of the right lung, and extended into the thoracic wall, the diaphragm, and the heart. No evidence of tumor metastases was found outside the thoracic cavity. The brain showed acute hypoxic injury of the hippocampus although no thrombusA thrombus is a solid mass resulting from the aggregation of blood constituents within the vascular system. was found.
Asbestos has been identified as a risk factor for developing:
- localized fibrous plaques or, rarely, diffuse pleural fibrosis;
- pleural effusionsPleural effusion is the presence of fluid in the pleural space. Increased hydrostatic pressure in the pulmonary vasculature, as seen in heart failure, is one cause of pleural effusion.;
- parenchymal interstitial fibrosis (asbestosis);
- bronchogenic carcinoma;
- mesotheliomas; and
- laryngeal and perhaps other extrapulmonary neoplasms, including colon carcinomas.
- What is the most common tumor produced by asbestos and what is the significance of both asbestos expose and smoking?
Bronchiogenic carcinoma is the most common tumor associated with asbestos (five times increased risk after asbestos exposure). However, the risk for developing mesothelioma (which is normally an extremely rare tumor) increases by 1,000-fold after asbestos exposure.Concentration, size, shape, and solubility of the different forms of asbestos dictate whether disease will occur.
There are two distinct geometric forms of asbestos:
- serpentine (curly and flexible fibers), and
- amphibole (straight, stiff, and brittle fibers).
The serpentine chrysotile chemical form accounts for most of the asbestos used in industry.
Amphiboles, though less prevalent, are more pathogenic than chrysotiles, particularly with respect to induction of malignant pleural tumors (mesotheliomas). Indeed, some studies of mesotheliomas have shown the link is almost always to amphibole exposure.
Asbestos bodies appear as golden-brown, fusiform or beaded rods with a translucent center. They are composed of an asbestos fiber coated with an iron-containing proteinaceous material. They arise when macrophages attempt to phagocytose asbestos fibers; the iron (ferritin) binds to the fiber within the phagocyte. Other inorganic particles may also be incorporated onto the asbestos fiber along with the ferritin.
- eMedicine Medical Library: Malignant Mesothelioma Imaging
- eMedicine Medical Library: Asbestosis Imaging
- Merck Manual: Asbestos-Related Disorders
- Whitaker D. The cytology of malignant mesothelioma. Cytopathology 2000 Jun;11(3):139-51.
- Johnson JS, Edwards JM. Malignant mesothelioma mimicking squamous carcinoma in a pleural fluid aspirate. Cytopathology 2001 Feb;12(1):54A normal PaCO2 is 35 to 45 mmHg.-6.