Background: We compared SPECT and planar (99m)Tc-MIBI scintimammography (SMM) in the detection of primary breast cancer and metastatic axillary lymph node involvement, and the scintigraphic results with the histopathological/cytological findings.
Material and methods: 303 consecutive patients with 308 suspicious or indeterminate lesions observed in mammographies were entered in this study. After an intravenous injection of 740 MBq of (99m)Tc-MIBI, anterior supine, right and left lateral planar images in a prone position and a SPECT study were acquired.
Results: 85 malignant and 223 benign breast lesions were confirmed by histopathology/cytology. The overall sensitivity in the detection of breast cancer was 92% (78/85) for SPECT and 82% (70/85) for planar imaging (p = NS), respectively; overall specificity was 91% (204/223) for SPECT and 91% (202/223) for planar scans (p = NS), respectively. Metastatic axillary lymph node involvement was seen in 35 patients; per-axilla overall sensitivity was 66% (23/35) for SPECT and 54% (19/35) for planar images (NS), respectively; overall specificity was 76% (38/50) and 86% (43/50), respectively (NS).
Conclusions: Our results confirm the high diagnostic accuracy of (99m)Tc-MIBI scintimammography in the diagnosis of breast cancer, and show SPECT to be slightly more sensitive than planar imaging, especially in detecting malignant breast lesions. We found the sensitivity of both imaging modalities to be quite low in the detection of metastatic axillary lymph node involvement. SPECT provides additional information to planar SMM with respect to the localization of (99m)Tc-MIBI uptake and tumour extent and improves diagnostic certainty. Our experience suggests that SPECT combined with planar SMM should be used more widely.