Recurrent malignant phyllodes tumor of the breast: An extremely rare case of recurrence with only rhabdomyosarcoma components.

Rhabdomyosarcoma is a rare disease that typically occurs in children. Rhabdomyosarcoma seldom occurs in the breast, and its diagnosis and treatment have infrequently been reported. The present case is a rare one of a recurrent malignant phyllodes tumor of the breast with only rhabdomyosarcoma components. A 69-year-old woman received a diagnosis of borderline phyllodes tumor of the left breast and underwent partial mastectomy. During follow-up, a left breast mass was found 1 year and 8 months after the previous surgery. Based on examination findings, it was suspected to be recurrent phyllodes tumor, so total left mastectomy was performed in our hospital. After the surgery, immunostaining failed to determine the epithelial component which may be produced by the proliferative part of stromal cells of previous phyllodes tumors. However, we could not exclude the possibility that this was a new tumor. After comparing samples with specimens from the first operation, it was finally determined to be a malignant phyllodes tumor with a rhabdomyosarcoma component. Therefore, chemotherapy was given, and vincristine, actinomycin D, and cyclophosphamide therapy was introduced. At the same time, radiation therapy was planned. Among phyllodes tumors, cases involving rhabdomyosarcoma components are very rare, especially those where the recurrence morphology only shows the same rhabdomyosarcoma components. This was a rare case with unique characteristics and great reference value.