Growing Teratoma Syndrome: Illustrative Case Review

We present two cases of Growing Teratoma Syndrome (GTS), one in a male patient with testicular mixed germ cell tumor and the second one in a female patient with ovarian mixed germ cell tumor. During or after chemotherapy, both patients were found to have enlarging masses, despite a significant decrease in or normalization of serum tumor markers. These enlarging masses were resected in one patient and pathological examination confirmed mature teratoma with no viable germ cell tumor. These findings are consistent with growing teratoma syndrome. It is important to recognize the possibility of a growing teratoma syndrome in patients with mixed germ cell tumor and growing metastatic masses on imaging studies despite a significant decrease/normalizing serum markers since additional chemotherapy would be ineffective and surgery is the recommended treatment.