Test Catalog

Test ID: CALRC    
Calreticulin ex9mut Immunostain, Technical Component Only

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

Identifying the presence of CALR exon 9 frameshift alterations in myeloproliferative neoplasms

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

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

The detection of calreticulin exon 9 frameshift alterations can assist in the diagnosis and prognostication of myeloproliferative diseases. Although these alterations are heterogeneous, they all result in a protein with a novel 36-amino acid C terminus the anticalreticulin CAL2 clone specifically identifies.


Most patients with essential thrombocythemia or primary myelofibrosis not associated with Janus kinase 2 (JAK2) or MPL variants are associated with CALR exon 9 variants and primary myelofibrosis patients carrying CALR variants have a more indolent clinical course.

Interpretation Provides information to assist in interpretation of the test results

This test does not include pathologist interpretation; if an 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. 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

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. Vannucchi AM, Rotunno G, Bartalucci N, et al: Calreticulin mutation-specific immunostaining in myeloproliferative neoplasms: pathogenetic insight and diagnostic value. Leukemia. 2014 Sep;28(9):1811-1818. doi: 10.1038/leu.2014.100

2. Stein H, Bob R, Durkop H, et al: A new monoclonal antibody (CAL2) detects CALRETICULIN mutations in formalin-fixed and paraffin-embedded bone marrow biopsies. Leukemia. 2016 Jan;30(1):131-135. doi: 10.1038/leu.2015.192

3. Klampfl T, Gisslinger H, Harutyunyan AS, et al: Somatic mutations of calreticulin in myeloproliferative neoplasms. N Engl J Med. 2013 Dec 19;369(25):2379-2390. doi: 10.1056/NEJMoa1311347