Extrapulmonary hydatid cyst

Case contributed by Shimalis Tadasa Fayisa
Diagnosis certain


Chest pain for 2 months

Patient Data

Age: 65 years
Gender: Male

Well-defined non-enhancing cystic mass in the left posterior mediastinum between the T4 and T10 vertebral levels encasing the descending aorta and displacing the adjacent left lower lobe. The inferior portion and lateral wall of the cyst wall both exhibit localized regions of calcification. The left eighth rib's posterior arch has been destroyed in an expansile, lytic fashion.

Additionally, there is lytic destruction of the left pedicle of the eighth thoracic vertebra, as well as both transverse processes on either side and the posterior vertebral bodies of T7 and T8. Intervertebral extension with left neural foraminal enlargement and perineural fat effacement between T6-T7 and T8-T9.

Multiloculated non-enhancing cystic lesion extending from the chest wall superiorly into the soft tissues of the neck.

No pulmonary cyst is visible.

From chest wall


To maintain patient confidentiality, the pathology report's image was cropped and modified.


Gross: Grey white membranous tissue measuring 2 cm x 2 cm.

Microscopic: Histologic section shows thick fibrous fragments of tissue with intense foreign body type giant cells granuloma admixed with scattered small mature lymphocyte along with laminated glassy membranous tissue with central granular necrosis background.

Diagnosis: Posterior chest wall hydatid cyst (echinococcus).

Case Discussion

The above case shows extrapulmonary hydatid cyst involving the mediastinum, chest wall bone, and muscles, proven by biopsy.

Extrapulmonary hydatid cysts are uncommon but may develop as a result of hematogenous dissemination or direct extension from the lung, liver, or spleen to involve the mediastinum, vessels, skeletal structures, and the chest wall.

Mediastinal involvement can manifest as unilocular, multilocular or calcified cysts and frequently affects the anterior thymic area. It is typical to see neighboring bone involvement and soft tissue expansion.

Due to the absence of pericyst development, aggressive lesions can involve bone causing well-defined expansile multiloculated cystic lesions that can branch in an irregular fashion. Overlying soft tissue expansion demonstrates unilocular, multilocular or daughter cysts with or without calcification.

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