Variable somatostatin receptor subtype expression in 151 primary pheochromocytomas and paragangliomas

Area of Science:

• Endocrinology
• Oncology
• Molecular Pathology

Background:

• Pheochromocytomas (PHEOs) and paragangliomas (PGLs) are rare neuroendocrine tumors.
• These tumors express somatostatin receptors (SSTRs), forming the basis for current imaging and therapy.
• Variability in SSTR expression may influence treatment efficacy.

Purpose of the Study:

• To investigate the immunohistochemical expression of SSTR subtypes 1-5 in PHEOs and PGLs.
• To correlate SSTR expression with tumor characteristics, including metastatic potential and SDHB deficiency.
• To inform the development of targeted therapies and personalized treatment approaches.

Main Methods:

• Analysis of SSTR1-5 expression using immunohistochemistry in 151 primary PHEOs and PGLs.
• Inclusion of metastasized tumors (n=14) and SDHB-deficient tumors (n=16).
• Assessment of proliferation rate using MIB1 staining.

Main Results:

• SSTR2 and SSTR3 were the most abundant SSTRs; SSTR1, SSTR4, and SSTR5 showed limited expression.
• All metastatic PGLs (9/9) demonstrated strong SSTR2 positivity, contrasting with metastatic PHEOs (1/5).
• SSTR3 expression was reduced in metastatic tumors and those with high proliferation (MIB1 ≥ 5%).

Conclusions:

• SSTR expression profiles in PHEOs and PGLs are heterogeneous, necessitating individual tumor analysis.
• SSTR2 and SSTR3 are key subtypes, with SSTR2 particularly relevant in metastatic PGLs.
• Development of novel SSTR analogues targeting multiple SSTRs may benefit specific patient subgroups, enhancing personalized diagnostics and therapeutics.