INTRODUCTION: The lack of standardization to interpret scintimammograms directly influences the efficiency of the method. Small lesions can present localized low-intensity 99mTc sestamibi uptake, which can be classified as positive by some professionals and negative by others. Quantitative and semi-quantitative analyses of suspect lesions have been suggested as a technique of improving the accuracy of detecting breast tumors. Unfortunately, until now, there is no consensus about the best method to calculate an index of malignancy indicative values.
AIM: To measure the intensity of 99mTc sestamibi uptake in breast nodules.
PATIENTS AND METHOD: Indexes of uptake, calculated as counts/pixels observed in regions of interest identified on scintimammograms of suspect lesions and in the contralateral breast, were compared for 98 nodules with localized uptake of 99mTc sestamibi.
RESULTS: The mean of the indexes was significantly greater in malignant nodules (n = 93; I = 2.9 ± 1.73; p < 0.001), including ductal carcinomas (n = 83; I = 3.0 ± 1.79; p < 0.001) and lobular carcinomas (n = 03; I = 2.6 ± 0.65; p < 0.05) compared to benign nodules (n = 05; I = 1.6 ± 0.41). Mucinous carcinomas (n = 02; I = 2.1 ± 1.12), medullary carcinomas (n = 02; I = 1.7 ± 0.57) and papillary carcinomas (n = 01; I = 1.5) as well as high-risk intraductal lesions (carcinoma in situ) (n = 02; I = 1.7 ± 0.4) demonstrated lower indexes similar to indexes observed in benign nodules. The range of the index variations was greater for ductal carcinomas (1.0 - 11.0), compared to other lesions such as lobular (2.1 - 3.3), mucinous (1.3 - 2.9), medullary (1.3 - 2.1) high-risk intraductal lesion (1.4 - 2.0) and benign nodules (1.2 - 2.1).
CONCLUSIONS: Higher indexes are observed in malignant nodules, especially among ductal and lobular carcinomas. Indexes of less than 2.11 are unspecific and do not discriminate the nature of the nodule. As the index increases, the probability that the tumor is malignant also increases, with ductal carcinomas having the highest indexes.
