Background: Glycogen-rich (clear cell) carcinoma of the breast is an unusual variant of breast carcinoma that has been described only recently.
Cases: We report two cases of glycogen-rich carcinoma with the corresponding fine needle aspiration findings. Cytologically, the presence of a delicate/foamy to clear cytoplasm was the only feature identified to distinguish these tumors from the more common infiltrating duct carcinoma.
Conclusion: Cytologically, the characteristics were not distinctive enough to predict the clear cell nature of the tumor histology. Other breast carcinomas that show optically clear cytoplasm include lipid-rich, secretory, histiocytoid and signet-ring carcinoma. Some cytologic features distinguish them from glycogen-rich carcinoma. Clinical correlation would be required to exclude metastatic clear cell carcinoma from such primaries as the kidney.