Test Catalog

Test ID: RB1    
Retinoblastoma Protein (Rb) Immunostain, Tech Only

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

Aids in the identification of high grade neuroendocrine carcinomas and small cell carcinomas

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

Retinoblastoma (Rb) is a phosphoprotein that is expressed in most normal cells and acts as a tumor suppressor by providing a cell cycle checkpoint between G1 and S phases. Loss of nuclear expression of Rb is useful in the identification of neuroendocrine carcinomas and small cell carcinomas. Loss of Rb can also be helpful to differentiate spindle cell lipomas from myofibroblastomas and cellular angiofibromas from other genital stromal lesions.

Interpretation Provides information to assist in interpretation of the test results

This test includes only technical performance of the stain (no pathologist interpretation is performed). If diagnostic consultation by a pathologist is required order PATHC / Pathology Consultation.


The positive and negative controls are verified as showing appropriate immunoreactivity. If a control tissue is not included on the slide, a scanned image of the relevant quality control tissue is available upon request. Contact 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

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

1. Thunnissen E, Borczuk AC, Flieder DB, et al: The Use of Immunohistochemistry Improves the Diagnosis of Small Cell Lung Cancer and Its Differential Diagnosis. An International Reproducibility Study in a Demanding Set of Cases. J Thorac Oncol 2017 Feb;12(2):334-346

2. Yuan J, Knorr J, Altmannsberger M, et al: Expression of p16 and Lack of pRB in Primary Small Cell Lung Cancer. J Pathol 1999;189:358-362

3. Chen B, Marino-Enriquez A, Fletcher C, et al: Loss of Retinoblastoma Protein Expression in Spindle Cell/Pleomorphic Lipomas and Cytogenetically Related Tumors: An Immunohistochemical Study With Diagnostic Implications. Am J Surg Pathol 2012;36(8):1119-1128

4. Tang L, Basturk O, Sue J, et al: A Practical Approach to the Classification of WHO Grade 3 (G3) Well-differentiated Neuroendocrine Tumor (WD-NET) and Poorly Differentiated Neruoendocrine Carcinoma (PD-NEC) of the Pancreas. Am J Surg Pathol 2016;40(9):1192-1202

5. Konukiewitz B, Schlitter A, Jesinghaus M, et al: Somatostatin receptor expression related to TP53 and RB1 alterations in pancreatic and extrapancreatic neuroendocrine neoplasms with a Ki67-index above 20%. Mod Pathol 2017;1-12