Technetium-99m sestamibi scintimammography: the influence of histopathological characteristics, lesion size and the presence of carcinoma in situ in the detection of breast carcinoma

The limit of detection of invasive carcinoma by scintimammography appears to be >10 mm, but not uncommonly smaller invasive carcinoma is detected in the presence of pre-invasive carcinoma (carcinoma in situ). The aims of this study were to determine whether a relationship exists between the presence of carcinoma in situ and the detection of invasive carcinoma using scintimammography, and to further characterise the influence of lesion size and histopathological characteristics on the diagnostic accuracy of scintimammography for the detection of invasive breast carcinoma. One hundred and seventeen patients were studied prospectively by scintimammography, X-ray mammography and, where appropriate, breast ultrasound prior to excision biopsy of all suspicious breast masses (n=123, 93% palpable). Thirty-five of these patients had a history of previous ipsilateral breast carcinoma. Sixteen percent of biopsy specimens were benign. The remaining specimens were malignant or pre-malignant. The overall diagnostic sensitivity of scintimammography was 84% and the specificity was 80%. The overall sensitivity and specificity for X-ray mammography (n=123), including those examinations combined with breast ultrasound (n=76), were 73% and 69%, respectively. The maximum size of the measured invasive carcinoma ranged from 5 to 80 mm (median 20 mm), Although the maximum size detected for invasive carcinoma in the presence of carcinoma in situ ranged from 3 to 40 mm (median 20 mm), this difference was not statistically significant (P=1.10, t test). Seven cases of carcinoma in situ were not detected by scintimammography. The diagnostic sensitivity of scintimammography for the detection of invasive carcinoma was 98% for lesions 16-25 mm, 91% for lesions 11-25 mm, 78% for lesions >25 mm and 55% for lesions <11 mm. Scintimammography may offer increased diagnostic accuracy for the detection of breast carcinoma, thereby complementing anatomical imaging. This is particularly evident in technically difficult patients who have had previously treated breast cancer. There appears to be no difference in the diagnostic sensitivity of scintimammography for the detection of invasive carcinoma in the presence or absence of carcinoma in situ.