A Case of Echinococcal Cyst of the Lung

Echinococcosis, also known as Hydatid disease, is caused by the larvae of the tapeworm Echinococcus. It is globally prevalent and is a major clinical health concern. It is endemic in most underdeveloped regions including Asia, the Mediterranean, South America and Africa. There are four species within the genus Echinococcus, with E. granulosus and E. multilocularis being the most common, causing Cystic Echinococcosis (CE) and Alveolar Echinococcosis (AE). The clinical presentation of the disease is non-specific. It commonly involves the liver, lungs, brain and adrenal glands. Pulmonary disease is significant for its propensity to affect children and young adults. This young population accounts for ∼50% of pulmonary hydatid cysts [1]. Cysts are known to grow extensively in size. Many patients are asymptomatic and have only a solitary cyst. Symptoms arise from enlargement of the cyst and from eroding and pressure applied by the cyst to blood vessels and organs. If rupture of the cyst occurs it can lead to immunologic reactions such as asthma and anaphylaxis. Echinococcus in the lung can pose diagnostic dilemmas, as their homogeneous density and tendency to occur alone may cause them to be confused with squamous cell carcinoma, adenocarcinoma, solitary metastasis, and abscess [2]. Our case is of such a patient who was found to have a 6 cm mass in the right middle lobe (RML) found on a chest X-ray during evaluation of back pain. Echinococcus should always be included in a differential diagnosis of any mass lesions especially in immigrant populations from endemic countries.