Chapter 64: Pleural Diseases: Primary and Metastatic Malignancies

INTRODUCTION

Pleural malignant disease is a heterogeneous group of cancers that range from primary intrathoracic cancers such as mesothelioma to metastatic cancers from extrathoracic sources. Often found incidentally, pleural malignancies may present as small pleural effusions or asymmetric pleural thickening on a chest x-ray or CT scan. As disease progresses, tumor may decrease lung compliance by entrapment and fluid production causing pressure on other structures, leading to symptoms of chest pain, dyspnea, and cough. Goals of care depend on the type of malignancy (primary vs. metastatic) and the ability to control disease (small volume vs. large volume). Curative treatment may be possible in early-stage primary pleural cancers or in select cases of metastatic metastases, but often palliation is the true goal for most patients with pleural disease.

MALIGNANT PLEURAL EFFUSIONS

Background/Epidemiology

Malignant pleural effusions (MPEs) are often the first sign of a primary pleural malignancy or advanced extrathoracic cancer. In this section, we focus on MPEs that represent stage IV cancers that have spread to the pleural space and indicate M1 disease. Later in this chapter we will discuss MPEs related to primary mesothelioma. MPEs are extremely common with an estimated 1 million effusions occurring each year in the United States, with up to a quarter of those being malignant.¹ The median survival after diagnosis with an MPE is 4 months, with the most common cancers that cause MPEs, lymphoma, lung, breast, ovarian, and gastrointestinal cancers.² Regardless of the etiology, finding an MPE is a poor prognostic sign and goals of treatment should be focused on palliation.³

Pathology

The presence of cancer cells in the pleural fluid defines an MPE.² Cancers may spread to the pleura hematogenously, through lymphatics, or by direct extension. Malignant effusions are associated with an exudative process which is driven by two different mechanisms. First, tumor deposits established along the pleural membrane obstruct lymphatic flow. Second, implants stimulate the release of chemokines that promote increased vascular and pleural permeability allowing the leakage of larger proteins.¹

Clinical Manifestations

The advancing pathologic process may decrease lung compliance by entrapment and invasion of local structures, leading to the development of chest pain and dyspnea. Other signs include cough, anorexia, and weight loss. Physical exam findings may include decreased breath sounds and dullness to percussion.

Prognosis

The prognosis of patients with MPEs is extremely poor, with a median survival being 4 months.³ This estimate should guide treatment and focus interventions on symptom control.

Diagnostic Evaluation

Every patient with an MPE should undergo a history and physical. The history may identify risk factors such as exposure to occupational hazards, smoking, personal and family history of malignancies, and the presence of constitutional signs ...