Technetium-99m-sestamibi uptake in breast tumor and associated lymph nodes

The aim of this study was to measure the accumulation of 99mTc-sestamibi in breast tumors and their axillary lymph nodes in patients undergoing scintimammography.

Eighteen patients who were scheduled for breast surgery underwent scintimammography with 740 MBq of 99mTc-sestamibi on the day before the operation. The next morning, reinjection with 370 MBq was performed. Immediately after the surgical procedure, the 99mTc activity of the tumor samples and, when available, the related lymph nodes was measured in a gamma counter. The samples were weighed and prepared for histological analysis. The activity of each sample was normalized to the mean activity of normal tissue samples obtained from the same patient.

Among the 198 samples analyzed, the relative uptake of sestamibi was increased in 111 containing normal lymph nodes (1.80+/-0.79 vs 1.00+/-0.22, p<0.05), as well as in the seven containing invaded lymph nodes (2.01+/-0.83, p<0.01) and more dramatically, in the 22 with a carcinoma (5.64+/-3.06, p<0.001). In two patients with a benign lesion, both scintigraphy and counting demonstrated increased activity in the tumor. Four patients had negative scan results despite the presence of malignant tumor and a more than fourfold increase of sestamibi concentration in two of them.

Technetium-99m-sestamibi concentrates strongly in breast carcinoma, sometimes even when the scan results appear normal, and mildly in lymph nodes, especially when invaded; it also concentrates in some benign tumors, possibly in relation to the presence of epithelial hyperplasia.