**1. Introduction**

Hydatidosis is a parasitic disease caused by the Echinococcus larvae. There are four species of worms responsible for the presence of this disease in humans; however, the most frequent ones that cause cystic echinococcosis are granulosus, 95% of cases, and multilocularis. Echinococcus is a zoonotic disease requiring two mammals, one intermediate host (sheep or cattle) and the definitive host in dogs, wolves or foxes [1].

Batsch first described the form of Echinoccocus granulosus in 1786 and the first case described in the literature of a hydatid cyst is attributed to Bremser in 1821 [2]. In 1908, Rudolphi published a parasitology treaty where the term of hydatid cyst was first used [3]. In most cases, the primary localization of hydatid cysts is in the liver (60–80% of cases) with the lung being the second most common location (10–30%). In the remaining 10–15% of cases, either by haematogenous or lymphatic dissemination or through the veno-venous anastomosis of the Retzius space, the parasite can be found in any organ, tissue or cavity [4]. Primary pleural hydatid cyst is a very rare occurrence and is most often solitary [5].

Human contamination occurs by ingestion of parasite eggs by contaminated food, water or direct contact with the host. Even if hydatid cysts can develop anywhere in the body, liver and lung development are the most common. Pleural hydatidosis is a very rare disease, most cases being secondary to peripheral lung cysts that rupture or herniate in the pleural cavity.

Primary pleural hydatid cysts fall under the category of extra-pulmonary intrathoracic cysts, alongside those found in the parietal pleura, mediastinum, pericardium, diaphragm, fissures and chest wall, by either lymphatic or hematogenous dissemination.
