Scintimammography with 99mTc-MDP in the detection of primary breast cancer

The diagnostic accuracy of scintimammography with 99mTc-MDP was evaluated in 400 consecutive women with clinical or mammographic suspicion of breast cancer, candidate to surgery and/or excisional biopsy. Lateral views of both glands were acquired, in prone position, 5-10 min after the injection of 550-740 MBq of 99mTc-MDP. The scintigraphic results were compared to mammograms and classified using the histological findings as gold standard.

Mammography was suggestive for cancer in 231 (57%), suspicious in 49 (12%) and indeterminate in 120 (31%) patients. Breast carcinoma was histologically proven in 330 women, benign breast diseases in 70. The tumor size ranged from 4 x 5 to 50 x 60 mm. 99mTc-MDP visualized as foci of increased uptake 305/330 cancers (92%). In particular, in women with indeterminate mammograms the SMM had a diagnostic accuracy of 84%, correctly characterizing 101/120 lesions. Twenty missed cancers had largest diameter < or = 10 mm, 5 < or = 15 mm. Lack of 99mTc-MDP uptake occurred in 64 out of 70 benign lesions. These lesions were classified as truly negative. Conversely, 3 fibroadenoma and 3 epithelial hyperplasia with moderate or severe atypia were falsely positive. The overall specificity was 91.5%; the accuracy was 92%, the positive and negative predictive values were respectively 98% and 72%.

The results obtained in this study suggest that 99mTc-MDP scintimammography accurately detects breast carcinomas with largest diameter > 10 mm; it differentiates malignant from benign lesions, and it shows promising insights in characterizing breast abnormalities mammographically indeterminate.