Somatostatin and dopamine receptor expression in neuroendocrine neoplasms: correlation of immunohistochemical findings with somatostatin receptor scintigraphy visual scores

Summary Context The expression of somatostatin (sstr1‐5) and dopamine ( DR ) receptors in neuroendocrine neoplasms ( NEN s) facilitates diagnosis by tumour visualization with somatostatin receptor scintigraphy ( SRS ) and directs towards specific treatment with peptide receptor radionuclide therapy ( PRRT ) with radiolabelled somatostatin analogues. Objective To investigate the co‐expression of sstrs, D2R in relation to pre‐operative SRS s in NEN s. Design Prospective two‐centre study. Patients and measurements We analysed pre‐operative SRS of 60 patients [44 with gastrointestinal ( GI ) NEN s and 16 with lung NEN s] and compared SRS results with immunohistochemical ( IHC ) reactivity for sstr2, sstr3, sstr5 in sample tissues from primary ( n  = 54) and metastatic ( n  = 27) lesions and IHC reactivity for D2R in 23 samples from primary GI ‐ NEN s lesions. Results Sstr2 was the commonest sstr expressed (65·4%) and was co‐expressed with sstr3 and sstr5 in 32·1% and 24·7% of the specimens, respectively. In 67 of 81 specimens (82·7%), there was concordance of sstr2 immunohistochemistry with SRS findings ( P  < 0·001). D2R was expressed in only 8 of 23 (34·8%) GI ‐ NEN s while was co‐expressed with sstr2 in all cases. SRS grade, as per Krenning scale, was higher in metastatic foci, large‐size (>2 cm) tumours and GI ‐ NEN s, whereas sstr2 intensity was greater in GI compared to lung NEN s. SRS grade showed higher correlation with sstr2 ( r  = 0·6, P  < 0·001) and D2R ( r  = 0·5, P  < 0·001) IHC intensity scores than tumour size ( r  = 0·4, P  < 0·001) and sstr3 ( r  = 0·4, P  < 0·001) intensity score. Conclusions Sstr2 IHC expression and SRS are useful tools for the diagnosis and management of NEN s because they display a high concordance. IHC expression of DR 2 seems to be of potential clinical significance in GI ‐ NEN s tumours.