Metastatic cystosarcoma phyllodes: a light and electron microscopic study.

Two cases of metastatic cystosarcoma phyllodes, one in lung and the other in axillary lymph nodes, were studied with the light and the electron microscopes. The malignant element of these tumors appears to be a poorly differentiated mesenchymal cell. No evidence supporting the presence of epithelial cells was found. The tumor metastatic to the axilla exhibited intracellular virus-like particles similar to those described in adenocarcinoma of breast and other sarcomas.