ABSTRACT
A hibernoma is an uncommon benign soft tissue tumor composed of brown adipose cells; the mediastinal location as presentation is scarce, with only six cases previously reported. The diagnosis of hibernoma is challenging and must be made based on the clinical, radiographic, and cytologic features. Here we present a 33-year-old woman without any relevant medical history presented for outpatient evaluation of a dry cough persisting for three months, and the X-rays revealed a dense well-defined mass with smooth borders in the left upper posterior mediastinum. Posterior mediastinal lesions represent a relatively small proportion of patient loads in thoracic surgery and account for a total of 25% of the cases, with neurogenic tumors among the most frequently seen in adults. Of these, the nerve sheath tumors (schwannoma, neurofibroma, paraspinal ganglioneuroma) are the most seen. Other differential diagnoses of paravertebral masses are the paraspinal abscess, metastases, hematoma, descending aortic aneurysm, among others. The patient underwent surgical resection via left posterolateral thoracotomy, without complications.