The growing teratoma syndrome.

Six patients with metastatic mixed germ-cell tumors who had been treated successfully with chemotherapy had recurring solitary enlarging masses. Four had enlarging pulmonary masses and two patients had enlarging abdominal masses. Each had the presumed chemotherapy refractory mass surgically resected and was found to have mature teratoma with absence of malignant histologies. The growth in two patients can be attributed to tense and expansile cysts; the remaining four had firm masses. All patients remain free of disease without further therapy at 5, 13, 14, 25, 66, and 108 months. Early recognition of this previously unreported and unusual clinical circumstance of a benign teratoma to grow after chemotherapy will allow for surgical salvage.