Fibrous solitary tumor, a rare and ubiquitous neoplasy.

Fibrous solitary tumors (FST) are mesenchymal tumors that can appear in different body regions. It is estimated that around 30% are found in the thoracic region, while rarely in meninges, abdomen, pelvis, extremities and bones. A correct diagnosis is important because 15-20% of cases develop a malignant behavior.