Malignant phyllodes tumor composed almost exclusively of a fibrosarcomatous component: a case report and review of malignant phyllodes tumors with metastases

Here we present a case of malignant phyllodes tumor which was composed almost exclusively of a fibrosarcomatous component. A 52-year-old Japanese female noted a rapid increase of her right breast tumor. On admission, multiple lung metastases were detected by imaging. Right simple mastectomy was performed. The tumor, 10 × 10 cm in the largest dimension, had somewhat of a pushing margin, and showed a flesh-like appearance with marked necrosis. Microscopically, the tumor showed proliferation of atypical ovoid- or spindle-shaped cells in a myxoid matrix. Multiple sectioning revealed that the tumor had only focal occurrence of elongated tubular structures, and the occurrence of a small component of benign phyllodes tumor, leading to the aforementioned final diagnosis. Spindle cell carcinoma was excluded on the basis of the HE findings and the lack of immunoreactivity for cytokeratin when using a broad spectrum antibody mixture. Although the patient received adjuvant chemotherapy, no responsiveness was obtained. The patient died 4 months following surgery. We reviewed 15 malignant phyllodes tumors with metastases reported in Japan. The estimated 2.2-year survival rate following detection of metastasis was 11%, thus confirming the aggressiveness of the disease.