Differential expression of somatostatin receptors 1–5 in neuroendocrine carcinoma of the lung

The majority of neuroendocrine carcinomas (NECs) express somatostatin (SST) receptors (SSTRs). However, the expression of all 5 SSTR subtypes in pulmonary NECs has not been reported. We performed immunohistochemical analysis of all 5 SSTR subtypes (including the SSTR2A and 2B isoforms). In typical carcinoids, immunoexpression of SSTR 1, 2A, 2B, 3, 4, and 5 was observed in 47/56 (79.7%), 57/58 (96.6%), 39/59 (66.1%), 28/57 (49.1%), 3/58 (5.2%), and 0/57 cases, respectively. In atypical carcinoids, immunoexpression of SSTR 1, 2A, 2B, 3, 4, and 5 was observed in 7/9 (77.8%), 7/9 (77.8%), 7/9 (77.8%), 3/9 (33.3%), 0/9, and 0/9 cases, respectively. In large cell NECs, immunoexpression of SSTR types 1, 2A, 2B, 3, 4, and 5 was observed in 12/20 (60%), 12/20 (60%), 6/20 (30%), 8/20 (40%), 0/20, and 3/20 (15%) cases, respectively. In small-cell carcinomas, immunoexpression of SSTR types 1, 2A, 2B, 3, 4, and 5 was observed in 16/54 (27.6%), 40/56 (69%), 14/56 (24.1%), 9/56 (15.5%), 0/58, and 2/55 (3.4%) cases, respectively. Except for SSTR5, all SSTRs showed a tendency toward decreased expression in well- to poorly differentiated NECs. We believe that these findings indicate important implications for the future of SST analog therapy.