Chylothorax in a patient with metastatic Kaposi sarcoma: Differential diagnostic considerations

Kaposi sarcoma (KS) is a low-grade mesenchymal tumor involving blood and lymphatic vessels. There are four types, based on clinical presentation: classic, endemic (Africana), iatrogenic (typically, involving renal allograft recipients), and AIDS-associated (epidemic). Kaposi's sarcoma-associated herpes virus infection has been linked along with other factors to the development of KS. The Kaposi's sarcoma-associated herpes virus interacts and encodes for numerous molecular proteins that play a role in the pathogenesis of KS, including latency-associated nuclear antigen, viral G protein-coupled receptor, viral FLICE inhibitory protein, and viral IL-6. KS primarily affects the skin and causes disseminated disease in a variety of organs. Involvement of visceral organs other than the lining of the alimentary tract is extremely rare. While the chylous pleural effusions of KS may resemble other pulmonary diseases (including lymphangioma, lymphangectasis, and lymphangioleiomyomatosis) with chylous effusions at thoracic CT, differentiating features may allow for more prompt diagnosis and treatment. The presumptive diagnosis of AIDS-related pulmonary KS is often clinical. A tissue diagnosis is not required to establish the diagnosis of pulmonary KS. There are a variety of causes of chylothorax. The primary finding is a near-water-attenuating pleural effusion. The secondary findings of chylothorax can help differentiate the etiology.