Somatostatin receptor tissue distribution in lung neuroendocrine tumours: a clinicopathologic and immunohistochemical study of 218 'clinically aggressive' cases.

BACKGROUND: The management of pulmonary neuroendocrine tumours (NETs), with special reference to clinically aggressive carcinoids and large-cellneuroendocrine carcinomas (LCNECs), is poorly standardised and data about somatostatin receptor (SSTR) expression or therapeutic guidelines for somatostatin analogue administration are still debated. Materials and methods: A series of 218 lung NETs [24 metastatic typical carcinoids (TCs), 73 atypical carcinoids (ACs), 60 LCNECs and 61 surgically resected small-cell lung carcinomas] were investigated for SSTR types 2A and 3 tissue distribution using immunohistochemistry, in correlation with clinicopathologic parameters, outcome, scintigraphy and treatment. RESULTS: SSTRs were heterogeneously distributed with a significant progressive decrease from low- to high-grade forms. SSTR type 2A was strikingly overexpressed in metastatic TCs as compared with ACs and clinically benign TCs. SSTR tissue immunolocalization correlated with octreotide scintigraphy in 20 of 28 cases. CONCLUSION: The immunohistochemical determination of SSTRs, with special reference to low-grade/intermediate-grade tumours, may assist the clinical approach with somatostatin analogue-based diagnostic and therapeutic procedures in clinically aggressive pulmonary NETs.