Malignant phyllodes tumor with chondrosarcomatous differentiation: radiological-pathological correlation.

We present a case of a 63-year-old woman with malignant phyllodes tumor in her left breast. On imaging, a large, dumbbell-shaped, predominantly cystic mass with thin peripheral enhancement was noted. The lesion was causing rib destruction, chest wall invasion, and intrathoracic extension. These aggressive imaging features were considered highly suspicious of a malignant chest wall tumor. Subsequent chest wall resection of the tumor showed breast tissue with a biphasic lesion composed of proliferated spindle cells in loose sheets with extensive islands of atypical cartilage and a scanty epithelial component, including compressed ducts in the periphery of the lesion. A diagnosis of a malignant phyllodes tumor with stromal overgrowth and chondrosarcomatous differentiation was made in view of the presence of a benign epithelial component and negative reaction of the stromal component with a pancytokeratin. To the best of our knowledge, a phyllodes tumor with the radiological features of chest wall invasion and intrathoracic extension has not been described in the literature until now. Malignant phyllodes should be included in the list of differentials along with sarcomas on encountering lesions with such aggressive imaging features.