18-fluorodeoxyglucose positron emission tomography in cystic carcinoma of the breast.

Cystic infiltrating ductal carcinoma of the breast is uncommon and frequently misdiagnosed because of the predominant cystic presentation clinically. Three premenopausal patients presented with huge cystic breast lesions measuring 10, 19, and 20 cm for 12-, 6-, 10-months duration, respectively. In the first patient, mammography showed a high-density, well-circumscribed huge breast mass, whereas in the other two patients mammography was not possible because of the huge breast size. In all three patients, breast ultrasound showed large cystic lesions suggestive of tumor with central necrosis or bleeding from which a variable amount (270, 1300, 600 ml) of bloody fluid was aspirated, respectively. In the first two patients, cytologic examination of the aspirate showed evidence of malignant cells, whereas the third patient was diagnosed by histologic examination of the cyst wall biopsy. In all three patients, a whole-body positron emission tomography (PET) scan showed intense focal 18-fluorodeoxyglucose (FDG) breast uptake corresponding to the solid component and a ringlike uptake corresponding to the cystic component most likely representing tumor necrosis, hemorrhage, or both. Furthermore, whole-body PET scan was valuable in predicting the response to chemotherapy, characterizing the pelviabdominal mass and detecting the presence of hepatic and spinal metastases in the three patients, respectively. 18-FDG PET scan can help characterize a cystic breast mass by identifying the extent of the cystic and the solid component. It is also useful in staging cystic infiltrating ductal carcinoma by detecting lymph node involvement as well as distant metastases.