Infiltrating lobular carcinoma of LUMB HER2+ subtype with rhabdoid feature coexisting with synchronous malignant transformation of phyllodes tumor: An exceedingly rare clinicopathological characteristic in Vietnam.

The transformation of a benign phyllodes tumor (PT) into a malignant PT and/or carcinoma is extremely uncommon. We present a case of a 66-year-old female with a huge mass on the left breast which was successfully removed by surgical resection. The pathological diagnosis was infiltrating lobular carcinoma with pure rhabdoid features and the malignant transformation of a benign phyllodes tumor. The first time this rare case was reported, it is demonstrated a special phenomenon through the synchronous transformation of PT grades and the carcinomatous transformation of PT.