The Problematic Interpretation of Foamy Cells in Breast Fine Needle Aspirates

BACKGROUND: Lipid-rich carcinoma and primary malignant fibrous histiocytoma (MFH) of the breast are rare tumors. Cytologically the presence of cells with foamy cytoplasm can cause diagnostic difficulties in both tumors. CASES: Fine needle aspiration was performed on two females with breast masses. The lipid-rich carcinoma showed cells with fine, variably sized vacuoles in the cytoplasm. The MFH smears showed large, histiocytelike cells with foamy cytoplasm, both mononucleated and multinucleated. CONCLUSION: When presented with cytologic smears showing foamy cells, in addition to the nature of the nucleus one must pay attention to the size and character of the cytoplasmic vacuoles to differentiate between sarcoma versus carcinoma.