Possible causes of chylothorax include anterior mediastinal masses (
mediastinal lymphosarcoma, thymoma), heart disease (cardiomyopathy, heartworm disease, congenital cardiac diseases, etc.), fungal granulomas, congenital abnormalities of the thoracic duct, and diffuse lymphatic abnormalities.
While most cranial
mediastinal masses are usually thymoma or
lymphosarcoma, other causes may include ectopic thyroid tissue, branchial cyst, chemodectoma, or thoracic wall tumor.