Radiolabelled somatostatin analogs for diagnosis and radio-guided surgery of neuroendocrine breast cancer undetectable with conventional imaging procedures

Some neoplasms are classified as primary neuroendocrine tumours (NETs) because of their positivity for neuroendocrine markers [chromogranins A and B (CgA, CgB) and neuron-specific enolase (NSE)]. Neuroendocrine differentiation has been reported, for example, in both "in situ" and infiltrating breast cancer. Diagnosis of NET is bio-humoral (CgA, NSE, synaptophysin) and instrumental. Even if the final diagnosis is made by open biopsy, radionuclide imaging using radiolabelled somatostatin analogs, such as In-111 pentetreotide, may detect neuroendocrine primary tumours and metastases before they become detectable using traditional and advanced imaging modalities [mammography (MX), ultrasound (US) and magnetic resonance imaging (MRI)]. When neuroendocrine breast lesions are not detectable, radio-guided surgery (RGS) is able to localise cancer. We report a case of a woman with a palpable lymph node in the left axilla. She underwent a US-guided lymph node biopsy, which was positive for massive metastases, probably of neuroendocrine breast origin. Mammary plus axillary US showed only lymphadenopathy in the left axilla. MX and breast MRI were negative. Neoplastic markers (CEA, CA 15.3, CA 125 and CA 19.9) were negative too. On the other hand, neuroendocrine markers (NSE and CgA) were positive. A whole body scintigraphic scan plus thorax and abdomen single photon emission computed tomography (SPECT) with In-111 pentetreotide (222 MBq; 6 mCi) showed an uptake in the left mammary gland. No other pathological localisations were observed. The day after the intravenous injection of In-111 pentetreotide, the patient underwent RGS breast tumour resection and left axillary lymphadenectomy. In conclusion, we would like to emphasise: (1) the role of radionuclide imaging for the detection of breast NETs in relation to conventional diagnostic procedures; (2) the role of RGS in localising and removing a non-palpable breast NET that was undetectable with the use of conventional imaging techniques.