Test ID: ISLET    
Islet 1 Immunostain, Technical Component Only

Useful For Suggests clinical disorders or settings where the test may be helpful

Identification of endocrine tumors

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

For the initial technical component only immunohistochemical (IHC) stain performed, the appropriate bill-only test ID will be reflexed and charged (IHTOI). For each additional technical component only IHC stain performed, an additional bill-only test ID will be reflexed and charged (IHTOA).

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Islet 1 is a homeobox-gene-related transcription factor involved in the development of the endocrine pancreas. Islet 1 is expressed in endocrine pancreas, subsets of neurons of the adrenal medulla, and dorsal root ganglion cell layers in the retina, the pineal gland, and some areas of the brain. Islet 1 is a useful marker as it is positive in the majority of pancreatic endocrine tumors.

Interpretation Provides information to assist in interpretation of the test results

This test does not include pathologist interpretation, only technical performance of the stain. If interpretation is required, order PATHC / Pathology Consultation for a full diagnostic evaluation or second opinion of the case.


The positive and negative controls are verified as showing appropriate immunoreactivity and documentation is retained at Mayo Clinic Rochester. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request; call 855-516-8404.


Interpretation of this test should be performed in the context of the patient's clinical history and other diagnostic tests by a qualified pathologist.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Age of a cut paraffin section can affect immunoreactivity. Stability thresholds vary widely among published literature and are antigen dependent. Best practice is for paraffin sections to be cut within 6 weeks.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Du A, Hunter CS, Murray J, et al: Islet-1 is required for the maturation, proliferation, and survival of the endocrine pancreas. Diabetes. 2009;58:2059-2069. doi: 10.2337/db08-0987

2. Schmitt AM, Riniker F, Anlauf M, et al: Islet 1 (Isl1) Expression is a reliable marker for pancreatic endocrine tumors and their metastases. Am J Surg Pathol. 2008;32(3):420-425. doi: 10.1097/PAS.0b013e318158a397

3. Albarello L, Zerbi A, Capitanio V, et al: Transcription factors islet-1, Pax6, Nkx6.1, MafB and Pdx-1 in pancreatic endocrine tumors. JOP. 2008;9(6) Supplement:773

4. Koo J, Mertens R, Mirocha J, et al: Value of islet 1 and PAX8 in identifying metastatic neuroendocrine tumors of pancreatic origin. Mod Pathol. 2012 Jun;25:893-901. doi: 10.1038/modpathol.2012.34