Not everything is as it seems: unilocular thymic mediastinal cyst, clinical case report

Abstract

Primary mediastinal cysts are benign malformative lesions that represent between 12% and 30% of mediastinal lesions within which thymic cysts are extremely rare. These cysts are usually incidental findings until due to their characteristics they represent some clinical-pathological component that is usually the cause of study or concern due to their similarity between malignant and benign entities. We present a clinical case of a mediastinal cyst located upper and middle that occupied a large part of the intertracheo cava window and displaced adjacent structures in a patient in whom a space-occupying lesion of tumor origin was initially suspected. She underwent successful surgical resection of the cyst by thoracoscopy. The cytological study reported the content as cloudy liquid, hemorrhagic spread with abundant cells with a hematolymphoid appearance, some of the polymorphonuclear neutrophil type and in the biopsy evidenced rubbery tissue with a cyst wall with a focal lining of squamous epithelium without atypia that required immunohistochemistry to definitive classification whose final anatomopathological diagnosis consisted of a unilocular thymic cyst.