Glycogen-rich clear cell carcinoma of the breast: report of a case with fine-needle aspiration cytology and immunocytochemical and ultrastructural studies.

Fine-needle aspiration cytology, immunocytochemistry, and electron microscopic findings are described in a case of glycogen-rich clear cell carcinoma of the breast. The aspirate contained many small and large papillary cell groups and numerous single tall columnar cells with apical cytoplasmic projections and mild to moderate degree of nuclear pleomorphism. Cytochemical localisation of glycogen and immunostaining on air-dried smears with CEA and actin monoclonal antibodies permitted the correct identification and differential diagnosis of the tumor. Electron microscopic examination of the resected specimen confirmed the diagnosis of glycogen-rich clear cell carcinoma. The differential diagnosis and potential diagnostic pitfalls are discussed, and recommendation are offered to prevent misdiagnosis.