Phyllodes tumor metastasis to the tonsil with synchronous undifferentiated carcinoma

INTRODUCTION: Breast tumor metastasis to the tonsil is extremely rare. PRESENTATION OF CASE: A 54-year-old woman underwent resection of a breast malignant phyllodes tumor and later presented with metastasis to the lung and the left tonsil. She underwent left lower lobectomy and resection of the left tonsillar tumor. She subsequently developed undifferentiated carcinoma of the right tonsil. She underwent resection of the right tonsillar tumor and chemotherapy was started. The central venous catheter became infected with methicillin-resistant Staphylococcus aureus. Finally, she died. DISCUSSION: To the best of our knowledge, this is the first reported case of a phyllodes tumor metastasizing to the tonsil. Furthermore, morphological and immunohistochemical study revealed that the right tonsillar tumor was irrelevant to the phyllodes tumors. CONCLUSION: We report a case of phyllodes tumor metastasis to the left tonsil which developed undifferentiated carcinoma in the other side of tonsil later. Breast tumor metastasis to the tonsil is rare but it should be considered as a possible diagnosis.