Technetium-99m-MIBI scintimammography in palpable and nonpalpable breast lesions.

UNLABELLED: The aim of this study was to determine the diagnostic accuracy of 99mTc-MIBI scintimammography in patients with palpable and nonpalpable breast cancer.

METHODS: One hundred and forty patients with a clinically palpable breast mass and/or suspicious mammographic finding had prone scintimammography after the intravenous injection of 740 MBq 99Tc-MIBI within 5 days before open biopsy or surgery. All patients had mammography within 2 mo before the scintimammography. The mammography was read as probably benign, probably malignant or indeterminate. The scintimammography was read as positive or negative for breast cancer. The scintigraphic studies were correlated with mammographic findings and with histopathology.

RESULTS: Histopathological studies showed that the mean tumor size for 61 palpable tumors was 2.57 cm with a range of 1-6 cm, and for 24 nonpalpable tumors the mean size was 1.34 cm with a range of 0.5-3 cm. Mammography had an overall sensitivity of 91.58% and a specificity of 42.87%; the sensitivity was 90.16% and 95.45% and specificity was 57.14% and 32.14% for palpable and nonpalpable tumors, respectively. Eight cases were considered indeterminate. Scintimammography was true-positive for 71 breast cancers, true-negative for 47, false-positive for 8 and false-negative for 14. The overall sensitivity was 83.5% and the specificity 85.4%. In the patients with palpable masses, sensitivity was 95.1% and specificity 75%; in those with nonpalpable lesions, sensitivity was only 54.2% and specificity, 93.5%. Among 18 cases of palpable abnormalities with probably benign mammography, six had true-positive scintimammography. Of eight patients with indeterminate mammography, one was true-positive on scintimammography.

CONCLUSION: Scintimammography is an accurate and clinically useful tool for evaluating patients with palpable breast abnormalities when mammography is negative and in the cases of indeterminate mammography. A significant improvement in lesion detectability is necessary in nonpalpable breast abnormalities.