title: Somatostatin receptor type 2A immunohistochemistry in neuroendocrine tumors: a proposal of scoring system correlated with somatostatin receptor scintigraphy.
abstract: Typing somatostatin receptor expression in neuroendocrine tumors is of relevance to target somatostatin analogue-based diagnostic approach and treatment. The expanding use of immunohistochemistry to detect somatostatin receptors is to date not paralleled by an accurate methodological setting and standardized interpretation of the results. A multicentric study was designed to compare somatostatin receptor immunohistochemical expression with in vivo scintigraphic data and verify its usefulness in the clinical management of neuroendocrine tumors. After methodological setting by testing different somatostatin receptor antibodies, 107 cases of neuroendocrine tumors with available somatostatin receptor scintigraphy data and pathological material were retrospectively analyzed for somatostatin receptor types 2A, 3 and 5 immunohistochemical expression, and compared with scintigraphic images and, whenever available, with the clinical response to somatostatin analogue treatment. Restricting 'positive cases' to the presence of a membrane pattern of staining, an overall somatostatin receptor type 2A immunohistochemistry/somatostatin receptor scintigraphy agreement of 77% (chi2 test P<0.0001) was reached. Lower concordance ratios were detected in preoperative and metastatic tumor samples, possibly as a consequence of somatostatin receptor expression heterogeneity. Pure somatostatin receptor type 2A cytoplasmic staining showed poor correlation with somatostatin receptor scintigraphy (54% concordance rate). The immunohistochemical detection of somatostatin receptor types 3 and 5, which showed almost exclusively a cytoplasmic pattern, did not improve the concordance with scintigraphic data. In a pilot series, somatostatin receptor type 2A immunohistochemistry correlated with clinical response in 75% of cases. In conclusion, we propose a scoring system for somatostatin receptor type 2A immunohistochemistry in neuroendocrine tumors correlated with in vivo data, based on the evidence that only membrane (rather that cytoplasmic) staining should be considered for a reliable, standardized and clinically relevant report.
authors.affiliation: Department of Clinical and Biological Sciences, San Luigi Hospital, University of Turin, Orbassano, Turin, Italy. marco.volante@unito.it
authors.forename: Marco
authors.initials: M
authors.lastname: Volante
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Brizzi
authors.forename: Antongiulio
authors.initials: A
authors.lastname: Faggiano
authors.forename: Stefano
authors.initials: S
authors.lastname: La Rosa
authors.forename: Ida
authors.initials: I
authors.lastname: Rapa
authors.forename: Anna
authors.initials: A
authors.lastname: Ferrero
authors.forename: Gelsomina
authors.initials: G
authors.lastname: Mansueto
authors.forename: Luisella
authors.initials: L
authors.lastname: Righi
authors.forename: Silvana
authors.initials: S
authors.lastname: Garancini
authors.forename: Carlo
authors.initials: C
authors.lastname: Capella
authors.forename: Gaetano
authors.initials: G
authors.lastname: De Rosa
authors.forename: Luigi
authors.initials: L
authors.lastname: Dogliotti
authors.forename: Annamaria
authors.initials: A
authors.lastname: Colao
authors.forename: Mauro
authors.initials: M
authors.lastname: Papotti
mesh_terms: D006801:Humans; D007150:Immunohistochemistry; D018358:Neuroendocrine Tumors / Q000188:drug therapy / Q000378:metabolism*; D010865:Pilot Projects; D011877:Radionuclide Imaging; D017481:Receptors, Somatostatin / Q000378:metabolism*; D012680:Sensitivity and Specificity; D013004:Somatostatin / Q000031:analogs & derivatives / Q000627:therapeutic use
chemical_list: D017481:Receptors, Somatostatin; D013004:Somatostatin; C093733:somatostatin receptor 2