A 54-year-old woman comes to the office due to worsening nonproductive cough and dyspnea for the past several months. She also reports anorexia and an unintentional weight loss of 7 kg (15.4 lb). The patient has no prior medical conditions, takes no medications, and is a lifelong nonsmoker. Physical examination shows decreased breath sounds on the left side. Chest x-ray reveals a large left-sided pleural effusion. Thoracentesis yields fluid with a large number of red blood cells and numerous atypical cells staining positive for mucin. Which of the following is the most likely primary mechanism of this patient's pleural effusion?

Question

A 54-year-old woman comes to the office due to worsening nonproductive cough and dyspnea for the past several months.  She also reports anorexia and an unintentional weight loss of 7 kg (15.4 lb).  The patient has no prior medical conditions, takes no medications, and is a lifelong nonsmoker.  Physical examination shows decreased breath sounds on the left side.  Chest x-ray reveals a large left-sided pleural effusion.  Thoracentesis yields fluid with a large number of red blood cells and numerous atypical cells staining positive for mucin.  Which of the following is the most likely primary mechanism of this patient's pleural effusion?

Quizplus · Accepted Answer

11ec160b_3ce2_0754_9249_c115c49595c5_MD0001_00 This patient's several-month history of nonproductive cough, shortness of breath, and weight loss combined with a large left-sided pleural effusion on chest x-ray raises suspicion for malignancy. Thoracentesis yielding a high erythrocyte concentration (a common finding in malignant effusions) and atypical mucin cells is consistent with adenocarcinoma; lung adenocarcinoma and breast adenocarcinoma are 2 of the most common causes of malignant pleural effusion. Malignant effusions are exudative by Light criteria and can occur via several mechanisms: Localized lung inflammation can cause increased vascular permeability, resulting in increased inflow of fluid into the pleural space. Once malignant cells have metastasized to the pleural space, they can occlude the pleural lymphatic stoma located on the parietal surface and prevent pleural fluid reabsorption. This is likely the primary mechanism of effusion in this patient with evidence of pleural metastasis (ie, atypical mucin cells in pleural fluid). Disruption of the thoracic lymphatic duct is an occasional cause of malignant effusion that leads to a chylothorax (milky white pleural fluid with high triglyceride content). This mechanism is most commonly seen with lymphoma; it can sometimes occur due to mass effect of lung cancer on the thoracic duct, but this is relatively uncommon (Choice B). (Choice A) Decreased plasma oncotic pressure (ie, hypoalbuminemia) is a common cause of transudative pleural effusion. Although hypoalbuminemia due to malnutrition may complicate malignancy and could contribute to pleural effusion, it is unlikely to be the primary mechanism in this patient with evidence of pleural metastatic disease. (Choices C and D) Increased hydrostatic pressure in the pulmonary capillaries and intercostal veins can cause transudative pleural effusion in patients with decompensated heart failure or other causes of intravascular volume overload (eg, renal failure). Educational objective: Malignant pleural effusions are usually exudative by Light criteria and can occur via several mechanisms, including an inflammation-induced increase in vascular permeability (leading to increased inflow) and blockage of pleural fluid reabsorption by parietal pleura lymphatics (leading to decreased outflow). __________ References: Malignant effusion. (http://www.ncbi.nlm.nih.gov/pubmed/30137807)

A 54-Year-Old Woman Comes to the Office Due to Worsening