Giant cystic metaplastic carcinoma of the breast: a case report with diagnosis by fine needle aspiration

BACKGROUND: Breast cysts are mainly benign and are reported in association with fibrocystic disease and phyllodes tumor. Rarely have cystic changes been reported to occur in malignant tumors. They are usually small but large in rare cases. Giant breast cysts are very rare, and only a few cases have been reported. CASE: A 37-year-old woman presented with a rapidly growing breast mass. Mammography showed a huge, well-circumscribed cystic mass (17 x 16 x 16 cm) suggestive of a benign lesion. Cytologic examination revealed a highly cellular tumor composed of malignant cells of various sizes and shapes in a necrotic background. The smears were diagnosed as positive for malignancy and suggested metaplastic carcinoma. Mastectomy was performed, and histologic study confirmed the cytologic diagnosis. CONCLUSION: This is the first reported case of a breast cyst of this size. Clinically the cyst was confused with a benign lesion. The fine needle aspiration aided the diagnosis and planning of treatment.