The preoperative cytological diagnosis of malignant phyllodes tumor (MPT) is challenging due to the heterogeneity of its clinical, radiological, and morphological presentation. To better define the cytopathological characteristics of MPT, we reviewed 22 examples seen at the Institut Curie. The original cytologic diagnosis was benign breast tumor in four cases (18.2%), suspicious in seven cases (31.8%) (low-grade phyllodes tumor in six cases needing histological evaluation, suspicious of sarcoma in one case), and malignant in 11 cases (50%). Smears were composed of different proportions of clusters of epithelial cells (68.2%), phyllodes fragments (31.8%), spindle cells within stromal tissue (31.8%), isolated spindle-shaped or round cells (45.5%), and bipolar naked nuclei (22.7%). Giant cells and mitotic figures were also occasionally seen. The cytological findings on smears were correlated with histopathological observations. One of the difficulties to reach an accurate cytological diagnosis for MPT is the frequent overwhelming of clearly malignant sarcomatous cell by the presence of largely predominant clusters of epithelial cell.