Pathology

Abstract

Germ cell tumors (GCTs) are a group of benign or malignant tumors, presumably arising from primordial totipotential cells (see Chapter VI, “Genesis”). These tumors are derived from cell population within a normal embryonic stage of development. Primordial germ cells originate in the yolk sac endoderm and are visible in the developing embryo during the fourth week of gestation [43]. At six weeks, these cells migrate along the dorsal mesentery of the hindgut to the gonadal ridges where they populate either the developing ovary or testis. Although these cells are considered to be primarily gonadal in origin, GCTs are also found outside the testis or ovary. At the time of migration from the yolk sac to the genital ridge, some primordial germ cells may migrate away or arrest their course altogether and thus miss their intended destination. Tumors arising in extragonadal sites are mainly found in the midline, in the central neuroaxis such as the pineal region or the hypothalamus and neurohypophysis; elsewhere they can be found in the neck, the mediastinum, the retroperitoneum and the sacrococcygeal area. The mechanism of transformation of primordial germ cells into tumor growth is still obscure. DNA mutation, deletion, translocation during the cell cycle are all mechanisms by which transformation can occur [25] (see Chapter VI, “Genesis”). Abnormalities of chromosomes 1 and 12 have already been described in GCTs [7,37], and there is one reported case of germinomas in siblings [3] (see Chapter III “Epidemiology”).