Introduction: Cystosarcoma phyllodes are very rare tumors and may be difficult to diagnose clinically.
Background: Fibroadenomas have long been considered benign hyperplastic lesions rather than true neoplastic processes. However, previous clonality studies have shown differing results.
Aim: to assess diagnostic and treatment options for phyllodes tumor.
Materials and methods: A 41-year-old female patient undergoing assisted fertilization treatment. The patient underwent fine needle aspiration biopsy that confirmed fibroadenoma before the IVF attempt. At 17 weeks of gestation, due to an increase in volume of the fibroadenoma, an excisional biopsy was performer that showed a malignant phyllodes tumor. Then she underwent quadrantectomy and chemiotherapy After 1 year there was a recurrence of phyllodes tumors and she underwent mastectomy and chemotherapy.
Results: Fibroadenoma that was transformed into high-grade malignant cystosarcoma after ovarian stimulation, relapsed after one year and it was not immediately diagnosed. The patient underwent mastectomy and chemotherapy.
Discussion: it is difficult to diagnose recurrence and to determine tele frequency and the right treatment for such a rare cancer, so it is important to report any case in the literature.
Conclusions: We recommend to remove a fibroadenoma before attempting IVF for the risk of malignant transformation.