A Rare Case of Malignant Phyllodes Tumor of Breast Metastatic to the Skeletal Muscle

Malignant phyllodes tumors are rare fibroepithelial tumor accounting for 0.3 to 0.9% of all breast neoplasms. Distant metastasis occurs in 10-20% of patients, most common sites being the lung and bones. Skeletal muscle metastasis is rarely seen in malignant phyllodes. So far, only one case of malignant phyllodes tumor metastatic to skeletal muscle has been reported in the literature. A 45-year-old perimenopausal woman presented with a lump in her left breast and swelling over the right calf region. Workup showed mass in left breast and metastasis to the right calf muscle along with the lung and multiple bone metastases. She was started on ifosfamide- and adriamycin-based chemotherapy along with zolendronic acid. She received palliative radiotherapy to the spine and right calf region for pain. After 3 cycles, there was progression, so patient was started on second-line chemotherapy with gemcitabine and docetaxel. Patient developed severe pancytopenia after 3 cycles, so further chemotherapy was stopped as patient was not tolerating it.