To evaluate the value of 99m Tc-octreotide acetate (hereafter, 99m Tc-octreotide) somatostatin receptor (SSTR) scintigraphy in the detection of primary breast cancer and to correlate with expression of SSTRs.Fifty-four female and 1 male patients (range, 17–77 years; mean age, 48 years) with palpable breast lesion were included in this study. 99m Tc-octreotide and 99m Tc-MIBI scintigraphy were undertaken in all patients, and the region of interest was drawn around each lesion. Tumor uptake was measured and expressed as the ratio of tumor to normal tissue activity (T/NT). Final clinical diagnosis was confirmed by histopathological analysis. Expression of SSTR1–5 mRNA was measured with RT-PCR in 15 patients with malignant neoplasm, and protein level of SSTR-2 and SSTR-5 was measured using immunohistochemical staining in 15 patients with malignant neoplasm and 18 patients with benign lesion.Thirty-five patients were confirmed to have infiltrative ductal breast carcinoma, 1 patient with cellular cancer, 1 patient with adenocarcinoma and 18 patients had benign lesions. The sensitivity, specificity, positive predictive value and negative predictive value of 99m Tc-octreotide in detection of primary lesion were 91.8%, 22.2%, 71.8% and 57.1%, respectively. No significant correlation was observed between T/NT of 99m Tc-octreotide and 99m Tc-MIBI. SSTR mRNA subtypes were variably expressed. SSTR3 was the most highly expressed, followed by SSTR1, SSTR2 and SSTR5; SSTR4 was the least expressed in the level of mRNA of SSTR. Significant correlation was shown between T/NT and the expression of SSTR2 mRNA (r=0.73, P<.01). 99m Tc-octreotide acetate scintigraphy was sensitive for the detection of primary lesion of breast cancer; however, nonspecific breast tissue uptake hampered the specificity and clinical value in the detection of lymph node metastasis. Five subtypes of SSTR mRNA and protein SSTR2 and SSTR5 were expressed variably in breast cancer due to tumor heterogeneity. 99m Tc-octreotide imaging may hold promise in the evaluation of the level of SSTR2 in vivo.