Mediastinal germ cell tumours

Mediastinal germ cell tumours (MGCTs) are a heterogeneous group of neoplasias with assorted histological features; because of their heterogeneity and resemblance with other entities they often pose a diagnostic challenge for the pathologist.MGCTs are infrequent, histologically classified like other gonadal and extra-gonadal GCTs. MGCTs share with gonadal GCTs the isochromosome i(12p), and can be associated to gonadal dysgenesis; however, their mediastinal location is unique and therefore constitute a special group with distinctive pathogenesis, diagnostic approach and therapeutic schemes. Recent developments in genetics, cell biology and immunohistochemistry have disclosed interesting features in gonadal and extra-gonadal GCTs.Immunohistochemical studies are useful in the differential diagnosis of poorly differentiated metastatic tumours with occult primaries, to separate the types GCT, and to determine the lineage of somatic malignant transformation.