What happened, in summary

A 12-year-old girl was referred after earlier surgery for an abdominal mass. Her right ovary had been removed, but some tumor remained attached to the mesentery. Pathology confirmed a malignant ovarian germ cell tumor at Stage III. By the time she reached the specialist center, her abdominal swelling had returned and AFP and beta-hCG were markedly elevated.

She received 4 cycles of chemotherapy, but the abdominal mass continued to enlarge. Doctors changed to a second chemotherapy regimen, yet the mass kept growing after 2 more cycles and caused pain, pressure, and weight loss. At the same time, her tumor markers had nearly returned to normal.

The combination raised concern for growing teratoma syndrome rather than active cancer progression. She underwent wide surgical removal of the mass, and pathology showed mature teratoma.

She later completed 2 additional chemotherapy cycles in January 2025. At the latest follow-up, she had no evidence of disease and her tumor markers were normal. Her course shows how tumor growth and falling markers can point to a treatment-related transformation rather than worsening malignant disease.