Malignant Pleural Effusion

A collection of fluid in the pleural cavity result of

D.J. is a 64-year-old female with metastatic breast cancer. She initially was treated with a right modifi ed radical mastectomy followed by adjuvant chemotherapy with an anthracycline-based regimen. Repeat multiple gated acquisition scans demonstrated a left ventricular ejection fraction of 42%, so she was switched to cyclophosphamide, methotrexate, and 5-fl uorouracil (CMF). She denies any cardiac history and has remained active. She developed liver metastasis two years after completing adjuvant treatment and was placed on docetaxel, which she has tolerated well. D.J. presents at the clinic for her fourth cycle of CMF chemotherapy complaining of fatigue, a dry cough, and mild exertional dyspnea. On physical examination, her blood pressure is 130/82, apical pulse is 114, respiratory rate is 24 breaths per minute, temperature is 98.8ºF, and arterial blood oxygen saturation on room air is 98%. A complete blood count with differential, platelets, and electrolytes is within normal limits. Her lactic dehydrogenase (LDH) level remains high but stable at 643 IU/L, and her cancer antigen 15.3 level is 25% higher than the previous measurement. Physical examination reveals absent breath sounds and dullness on percussion over the lower right half of the chest.
A chest radiograph shows a collection of fl uid in the right chest. A lateral decubitus film is ordered and reveals free-flowing fl uid. Coagulation studies are within normal limits, and a thoracentesis is performed. Five hundred and fi fty ml of serosanguineous fl uid is removed and sent for laboratory analysis. D.J.'s pleural fl uid LDH is 500 mg/dl. Her ratio of pleural fl uid LDH to serum LDH is 0.8, and her pleural fl uid protein to serum protein ratio is 0.7. Her pleural fl uid pH is 6, carcinoembryonic antigen is 15 ng/ml, and red blood cell count is 120,000.
Several days later, the culture, gram stain, and cytology of the pleural fl uid are negative. D.J. is scheduled for further testing, including an echocardiogram and a computed tomography (CT) of the chest. The echocardiogram reveals no cardiac dysfunction and a left ventricular ejection fraction of 48%.
The CT of the chest shows a new 0.75 cm nodule in the right lower lobe of the lung. A needle biopsy is performed, and the pathology is consistent with breast cancer.

Pathophysiology
The space between the visceral pleura (i.e., lining of the lung) and the parietal pleura (i.e., lining of the thoracic cavity) is known as the pleural space. In healthy adults, about 10-50 ml of fl uid can be found in the pleural space. The fl uid lubricates the pleural layers, allowing them to move smoothly over each other. Fluid enters the pleural space in several ways: from the capillaries in the parietal pleura, via the interstitial spaces of the lung in the visceral pleura, and from the peritoneal cavity through small holes in the diaphragm (Light, 2001). Fluid is removed from the pleural space by means of capillaries in the parietal pleura or lymphatics, primarily the thoracic duct. As much as a liter of fl uid can move through the pleural space in a 24-hour period (Goldman, 2004).
A pleural effusion develops when either excess fl uid is formed in or decreased fl uid is removed from the pleural space. Nonmalignant factors associated with the development of pleural effusions include infection, drug reactions, and radiation therapy.
An MPE can occur as a result of the implantation of cancer cells on the pleural surface (e.g., solid tumors), leading to increased permeability of capillaries; the obstruction of lymphatics (e.g., lymphomas or breast cancer), preventing removal of fl uid; the obstruction of pulmonary vessels by a tumor (e.g., lung cancer); changes in the osmotic pressure of the pleural space because of the presence of malignant cells (e.g., lung or breast cancer); or the perforation of the thoracic duct (e.g., lymphoma) (Goldman, 2004;Huether & McCance, 2004;Muller, Fraser, Colman, & Pare, 2001). The obstruction of lymphatics is the leading cause of MPE. Pleural effusions are categorized by the characteristics of the pleural fl uid (see Figure 1), with most MPEs being exudative.
Lung cancer, breast cancer, and lymphoma are associated with 75% of MPEs. Effusions occurring in lung and breast cancer generally occur on the same side of the body as the primary lesion. Bilateral effusions usually are associated with liver metastases. About 30%