Germ cell tumors of miscellaneous extragonadal sites

Abstract

In this chapter we review the epidemiologic and clinicopathologic features of extragonadal germ cell tumors in locations other than mediastinum and the brain, with a special emphasis on their organ-related particularities and their differential diagnoses. Extragonadal germ cell tumors (EGCTs) represent 3.3 % of all germ cell tumors. In children and young adults, often these rare neoplasms are the result of neoplastic transformation of ectopic primitive germ cells entrapped during their migration toward the developing gonad (types I and II GCT). This explains their medial and paramedial locations and their reproducing both seminomatous and non-seminomatous tumors. However, in adults and older patients, many of them arise from cells similar to induced pluripotential somatic tumor stem cells present in somatic neoplasms of organs (type VI GCT), usually those of endodermal derivation such as the lung, stomach, liver, or urinary bladder, often reproducing non-seminomatous tumors such as yolk sac tumors and choriocarcinoma. GCTs developed in somatic neoplasms overlap significantly with the more common somatic malignancies of such organs.