Test Catalog

Test ID: CTNNB    
Beta-Catenin (CTNNB1) Mutation Analysis, Tumor

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

Distinguishing desmoid-type fibromatosis from other soft tissue tumors by assessing gene targets with in the BCAT (CTNNB1) gene


This test is not useful for hematological malignancies.

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

When this test is ordered, slide review will always be performed at an additional charge.

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

Desmoid-type fibromatosis is a locally invasive soft tissue tumor. The histological diagnosis of desmoid-type fibromatosis is challenging. Mutations in exon 3 of the beta-catenin (BCAT also known as CTNNB1) gene have been identified in 50% to 87% of desmoid-type fibromatosis, including T41A (121 A->G), S45P (133 T->C), and S45F (134 C->T), but not in other soft tissue tumors. Patients harboring beta-catenin mutations may have a higher recurrence rate compared to the patients with wild-type beta-catenin.


Next-generation sequencing has recently emerged as an accurate, cost-effective method to identify alterations across numerous genes. This test uses formalin-fixed paraffin-embedded tissue or cytology slides to assess for common somatic mutations in the beta-catenin gene known to be associated with desmoid-type fibromatosis. The results of this test can be useful for supporting a diagnosis of desmoid-type fibromatosis and predicting prognosis.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretative report will be provided.

Interpretation Provides information to assist in interpretation of the test results

An interpretive report will be provided.

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

This test cannot differentiate between somatic and germline alterations. Additional testing may be necessary to clarify the significance of results if there is a potential hereditary risk.


DNA variants of uncertain significance may be identified.


A negative (wild-type) result does not rule out the presence of a mutation that may be present but below the limits of detection of this assay.


Point mutations and small insertion/deletion mutations will be detected with in the BCAT (CTNNB1) gene only. This test does not detect large single or multiexon deletions, or duplications or genomic copy number variants.


Rare polymorphisms may be present that could lead to false-negative or false-positive results. Test results should be interpreted in the context of clinical findings, tumor sampling and other laboratory data. If results obtained do not match other clinical or laboratory findings, contact the laboratory for updated interpretation. Misinterpretation of results may occur if the information provided is inaccurate or incomplete.


Reliable results are dependent on adequate specimen collection and processing. This test has been validated on cytology slides and formalin-fixed, paraffin-embedded tissues; other types of fixatives are discouraged. Improper treatment of tissues, such as decalcification, may cause PCR failure.

Supportive Data

This next-generation sequencing assay detects somatic mutations that can be used to assist in the diagnosis of desmoid-type fibromatosis and predicting prognosis.


This assay has been shown to be very reproducible, having a 100% concordance for intra- and interassay reproducibility experiments. All somatic mutations that had been previously identified by various other molecular methods were detected by this assay during accuracy studies. No pathogenic variants were detected in known mutation-negative samples.

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

1. Lazar AJ, Tuvin D, Hajibashi S, et al: Specific mutations in the beta-catenin gene (CTNNB1) correlate with local recurrence in sporadic desmoid tumors. Am J Pathol 2008;173:1518-1527

2. Amary MF, Pauwels P, Meulemans E, et al: Detection of beta-catenin mutations in paraffin-embedded sporadic desmoid-type fibromatosis by mutation-specific restriction enzyme digestion (MSRED): an ancillary diagnostic tool. Am J Surg Pathol 2007;31:1299-1309

3. Domont J, Salas S, Lacroix L, et al: High frequency of beta-catenin heterozygous mutations in extra-abdominal fibromatosis: a potential molecular tool for disease management. Br J Cancer 2010;102:1032-1036

Special Instructions Library of PDFs including pertinent information and forms related to the test