Growing teratoma syndrome in intracranial non-germinomatous germ cell tumors (iNGGCTs): a risk for secondary malignant transformation—a report of two cases.

PURPOSE: About 5% of pediatric intracranial germ cell tumors and 20% of non-germinomatous germ cell tumors (NGGCT) progress to growing teratoma syndrome (GTS) following chemoradiotherapy. The growing teratoma is thought to arise from the chemotherapy-resistant, teratomatous portion of a germ cell tumor and is commonly benign but may undergo malignant transformation.

METHODS: Two pediatric patients whose intracranial NGGCTs progressed to growing teratomas during chemotherapy and later transformed to secondary malignant tumors after partial resection and radiation therapy (RT).

RESULTS: Both tumors were diagnosed by MRI scans and elevated serum and CSF markers. Following normalization of tumor markers with chemotherapy and initial decrease in tumor volume, subsequent imaging showed regrowth during chemotherapy with pathology revealing benign teratoma. RT was administered. Several years following this treatment, further growth was seen with pathology indicating malignant carcinoma in one patient and malignant rhabdomyosarcoma in the other. The patient with carcinoma received palliative care while the patient with the sarcoma received further resection, intensive chemotherapy, and an autologous stem cell transplant and is currently in remission, 36 months since malignant transformation.

CONCLUSION: Malignant transformation of presumed residual teratoma has been seldom reported. Treatment of NGGCT involves platinum-based chemotherapy with craniospinal RT and boost to the primary site, with cure rates of around 80%. Teratomas are characteristically chemotherapy and RT resistant and are treated surgically. In the event that residual or growing teratoma is suspected, a complete resection should be considered early in the management as there is a risk of malignant transformation of residual teratoma.