Growing teratoma syndrome.

Growing teratoma syndrome (GTS) is a rare clinical entity, which presents with enlarging teratomas masses of the retroperitoneum or other locations, occurring during or after systemic chemotherapy for the treatment of nonseminomatous germ cell of the testis (NSGCT), with normalised tumour markers. Awareness of this syndrome is necessary in order to prevent unnecessary chemotherapy and allow optimal management. Prognosis is excellent after the excision of these tumors, but surgery has to be as complete as possible.