**3. Clinical presentations**

Asymptomatic patients with either a malignant or a paramalignant effusion need not be treated initially [9]. Malignant pleural effusion will eventually develop into cancer in the majority of patients. It often recurs challenging the physicians, patients and the patient's family in balancing the benefits of symptomatic improvement with the risk and inconvenience of

Pathophysiology of MPE has not been fully understood yet and is still on debate. There are many hypotheses on the pathogenesis of MPE in cancer. It commonly results from disruption of normal starling forces regulating pleural fluid absorption by obstruction of mediastinal lymphatics, which drain the pleural space [9]. There is a strong relationship between media‐ stinal metastasis and development of MPE [12, 13]. Other causes of MPE include direct invasion (e.g. lung cancer, breast cancer, chest wall neoplasms), hematogenous spread of tumor to the pleura (eg, metastasis, non-Hodgkin's lymphoma), or increased capillary permeability caused by tumor invasion-related local inflammatory changes or vascular endothelial growth factor production [14]. Just the presence of metastasis does not seem sufficient to explain the pathogenesis of pleural effusions. In fact, only about 60% of patients with proven pleural

Indeed, the accumulation of excess pleural fluid associated with cancer may be the result of a number of separate factors in an individual patient [16]. Postmortem studies have demon‐ strated a strong relationship between carcinomatous infiltration of the mediastinal lymph nodes and the occurrence of pleural effusion [11,15]. This finding suggests an important role of the impaired lymphatic drainage in the pathogenesis of MPE. However, if this was to be the only mechanism, one would expect MPEs to be transudative, but instead, the majority of these

> Systemic effects of tumor Pulmonary embolism Hypoalbuminemia

Complications of therapy Radiation therapy (Early or late)

Chemotherapy

All fluids of pleura may not be malignant in patients with malignancy. The effusion caused by a neoplasm without the evidence of malignant cells in the pleural effusion as well as sur‐ rounding tissues is called as "paramalignant" effusion. Presence of paramalignant effusion is not a contraindication for the surgery. Obstructive pneumonia or atelectasia, lymphatic

therapy [10, 11].

86 Principles and Practice of Cardiothoracic Surgery

**2. Pathogenesis**

metastases develop pleural effusions [15, 16].

effusions are exudates [16].

Bronchial obstruction with pneumonia Bronchial obstruction with atelectasis

**Table 1.** The Causes of paramalignant Effusion [17]

Superior vena cava syndrome

Local effects of tumor

Lymphatic

Trapped lung Chylothorax

The first and most common presenting symptom is dyspnea (96%) [12, 18]. The pathogenesis of dyspnea caused by a large pleural effusion has not been clearly elucidated, but several factors may be involved including a decrease in the compliance of the chest wall, contralateral shifting of the mediastinum, a decrease in the ipsilateral lung volume, and reflex stimulation from the lungs and chest wall [19]. After other causes of dyspnea have been excluded; detailed anamnesis, physical examination and radiological monitoring are required. As many as a third of patients with malignant pleural effusions present with weight loss and cachexia and appear debilitated by chronic illness [20]. Malignant causes should be excluded firstly in the list of differential diagnosis in patients diagnosed as exudates. A complete medical history and physical examination should be done considering any potential causes or risk factors of malignancy.

Other bothersome symptoms are cough [44%) and chest pain (56%) [18]. The majority of patients with MPE are symptomatic while less than 25% have no respiratory complaints [12]. Other symptoms include sharp pleuritic pain, dull ache with a feeling of pressure, and heaviness in the chest. A physical examination can reveal decreased breath sounds, and dullness to percussion [12].
