Mediastinal germ cell tumors: a narrative review of their traits and aggressiveness features.

Objective: Mediastinal extragonadal germ-cell tumors (MEGCTs) are rare neoplasms with a multifaceted clinical behavior. This paper is devoted to review their main characteristics, including histological patterns and different factors of aggressiveness in MEGCTs. Proper understanding of the latter can help to better stratify patients' prognoses and improve clinical management. Background: Different theories exist on the origin of MEGCTs, including primordial germ cells deposition during embryogenesis. MEGCTs predominantly affects young males and aggressiveness follows the ability of local and systemic spread of each germ-cell neoplasia subtype, as well as their distinct responsiveness to therapy. Indeed, non-seminomatous MEGCTs have a worse prognosis. Unfortunately, they are also more frequent than seminomas in the mediastinum. Regardless of histological type, local aggressiveness can follow tumoral expansion with compression on or infiltration of mediastinal structures. Chemotherapy can be effective in reducing neoplastic volume, but different levels of sensitivity can be found in different MGCTs. In particular, a chemo-resistant teratoma component of a mixed MEGCTs can undergo a paradoxical enlargement after chemotherapy, while other components of the tumor regress. This is reflected by a concomitant normalization of serum tumoral markers and cardiopulmonary deterioration due to compression. Such clinical phenomenon, called growing-teratoma syndrome (GTS), requires a prompt surgical approach. Methods: A literature research of pertinent epidemiological, pathological and clinical articles was conducted. Conclusion: The mediastinum can harbor different kinds of neoplasia, including GCTs. The full spectrum of MEGCTs includes a variety of tumors with different clinical behaviors. Aggressiveness follows the inherent ability of local and systemic spread of each neoplastic type, as well as their distinct responsiveness to therapy.