Metastasis of Mammary Gland Malignant Phyllodes Tumor to the Mandibular Region: A Case Report and Review of the Literature

Phyllodes tumor is a rare breast tumor described by Müller (1938) as a lesion comprising leaflike stromal fibrous components and narrow cysts. The frequency of distant metastasis from this entity is reportedly approximately 20%, and no effective therapy has been established, so the prognosis is poor. This report describes the case of a 60-year-old woman with a history of left lung resection who showed metastasis of a mammary gland malignant phyllodes tumor to the oral cavity. Intraoral examination showed an elastic, hard mass measuring 28 × 27 mm in the gingiva around the left mandibular second molar. Biopsy examination showed growth of giant cells and roughly circular cells showing positivity for S-100, p63, and vimentin on immunohistochemical staining. The authors diagnosed metastasis of the mammary gland malignant phyllodes tumor to the left mandible and performed cyber knife irradiation (44 Gy in 5 fractions) of the left mandible. The mass in the oral cavity disappeared after cyber knife irradiation, but the patient died of direct invasion to the spine.