Sign in →

Test Code RB1 Retinoblastoma Protein (Rb) Immunostain, Tech Only

Advisory Information

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.

Shipping Instructions

Attach the green pathology address label and the pink Immunostain Technical Only label included in the kit to the outside of the transport container.

Specimen Required

Supplies: Immunostain Technical Only Envelope (T693)

Specimen Type: Tissue

Container/Tube: Immunostain Technical Only Envelope (T693)

Preferred: 2 unstained positively charged glass slide (25- x 75- x 1-mm) per test ordered; sections 4-microns thick

Acceptable: Formalin-fixed, paraffin-embedded (FFPE) tissue block

Secondary ID


Useful For

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

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
IHTOI IHC Initial, Tech Only No No
IHTOA IHC Additional, Tech Only No No

Method Name


Reporting Name

Retinoblastoma IHC, Tech Only

Specimen Type


Specimen Stability Information

Specimen Type Temperature Time Special Container
TECHONLY Ambient (preferred)

Reject Due To

Tissue/Other Wet/frozen tissue Cytology smears Nonformalin fixed tissue Nonparaffin embedded tissue Noncharged slides ProbeOn slides

Clinical Information

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.


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.

Clinical Reference

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

Day(s) and Time(s) Performed

Monday through Friday

Analytic Time

1 day

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

88342-TC, primary

88341-TC, if additional IHC

LOINC Code Information

Test ID Test Order Name Order LOINC Value
RB1 Retinoblastoma IHC, Tech Only Order only;no result


Result ID Test Result Name Result LOINC Value
604029 Retinoblastoma IHC, Tech Only Bill only; no result


If not ordering electronically, complete, print, and send a Immunohistochemical (IHC)/In Situ Hybridization (ISH) Stains Request (T763) with the specimen.