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

Abstract 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. M X 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.