Genomic features of mediastinal germ cell tumors: a narrative review

BACKGROUND AND OBJECTIVE: Germ cell tumors (GCTs) are uncommon malignancies generally originating from gonads. However, about 5% of GCTs arise outside the gonad (extragonadal), of which 80% develop from the mediastinum. While the prognosis of seminomas is not affected by the gonadal or extragonadal primary location, the prognosis of nonseminoma primary mediastinal GCTs (NS-PMGCTs) is poor, compared to its gonadal counterpart with an estimated 5-year overall survival of about 50%. The current treatments are sub-optimal to increase the cure rate of these rare GCTs. Therefore, molecular insights into these tumors would be valuable to develop novel therapies. The main objective of this review is to describe and dissect the genomic features associated with primary mediastinal GCTs (PMGCTs), highlighting the more frequent genomic alterations and their correlation with clinical outcomes. METHODS: We conducted a narrative review of the English literature available in PubMed and Google Scholar between 1982 and 2021, including meta-analyses, systematic reviews, case series and case reports regarding the genomic and clinical features of PMGCTs. We analyzed the available data to describe the molecular characteristics of PMGCTs compared to testicular GCTs (TGCTs), highlighting the most relevant biological and prognostic factors. KEY CONTENT AND FINDINGS: The high percentage of platinum resistance, the unique association with hematologic malignancies (HMs) and other malignancies, the higher prevalence of P53 mutations, and a distinct genomic landscape characterize this rare disease. CONCLUSIONS: Although some studies have unveiled recurrent molecular alterations in PMGCTs, few are particularly suitable for targeted therapy. Due to the rarity of PMGCTs, data sharing and the creation of an international consortium would be helpful to have a better understanding of the molecular drivers of these tumors.