Somatostatin receptor expression in thymic tumors.

Detection of thymic tumors by (111In-DTPA0)octreotide scintigraphy and the antitumor effect exerted by somatostatin (SS) analogs suggest significant expression of SS receptors (SSRs) in these tumors. We measured SSR subtype (sst)2A and sst3 expression by immunohistochemistry (IHC) in 14 thymic tumors previously studied by SSR scintigraphy (SRS). Scintigraphy showed significant (111In-DTPA0)octreotide uptake in 13/14 tumors (tumor-to-background ratios: 1.4- to 6-fold). By IHC, 4 tumors were positive for sst2A and sst3; two for sst2A and five tumors for sst3. Three tumors were completely negative. Overall, 11/14 (approximately 78% of cases) expressed at least one SSR subtype. Staining was highly heterogeneous: sst2A was confined to malignant epithelial cells or within stromal structures, and sst3 was predominantly associated with thymocytes. SRS provides immediate visualization of primary and metastatic lesions, while IHC reveals SSR subtype expression. This joined approach could help to select SS analogs beneficial for therapy.