Somatostatin Receptor 2A
Label Mnemonic: ISST2
Epic Lab Code: LAB8098
Downtime Form: A-1a Doctor/Provider Orders - Pathology Immunopathology
5238 RCP
Formalin Fixed, Paraffin Embedded Tissue containing Tumor (please specify case and block number on requisition)
Turn Around Time:
Within 5 days upon receipt
Reference Range:
An interpretive report will be provided.
Somatostatin receptors (SSTR) are highly expressed by neuroendocrine tumors, especially well-differentiated tumors. This high-level expression is the basis of nuclear medicine imaging of neuroendocrine tumors (e.g., OctreoScan) and, perhaps more importantly, anti- secretory and anti-proliferative therapy with somatostatin-analogues (e.g., octreotide). Of the various receptor subtypes, a positive scan is most closely related to expression of SSTR2A.

Octreotide therapy is only approved in the face of a positive OctreoScan or a positive SSTR2A immunohistochemical result. Unfortunately, the OctreoScan is often negative in tumors <2 cm, and occasionally tumors are resected before their neuroendocrine nature is known.

If >10% of tumor cells stain, the tumor is likely to express high levels of somatostatin receptors, and the patient may benefit from somatostatin-analogue therapy. If 1-10% of cells stain, the result is indeterminate. Patients with weak staining in this indeterminate group are unlikely to benefit from octreotide, as are patients with no staining at all.

Test results should be interpreted in the context of clinical findings and other laboratory data. Errors may occur in our interpretation of results if information given to us is inaccurate or incomplete.
Immunohistochemical staining is used to determine the presence or absence of protein expression for SSTR2A.
CPT Code:
SSTR2A - 88360