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Test ID: FUS    
Low-Grade Fibromyxoid Sarcoma (LGFMS), 16p11 (FUS or TLS) Rearrangement, FISH, Tissue

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

Supporting the diagnosis of low-grade fibromyxoid sarcoma when used in conjunction with an anatomic pathology consultation

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

Low-grade fibromyxoid sarcoma (LGFMS) is a rare malignant soft tissue tumor characterized by a bland fibroblastic spindle cell proliferation arranged in alternating fibrous and myxoid areas, with or without giant collagen rosettes. These tumors are characterized by the chromosome translocation t(7;16)(q33-34;p11), which results in the fusion of FUS (also called TLS) on chromosome 16 to CREB3L2 (also called BBF2H7) on chromosome 7. Greater than 70% of LGFMS are cytogenetically characterized by this translocation. In rare cases, a variant t(11;16)(p11;p11) has been described in which FUS is fused to CREB3L1 (OASIS), a gene structurally related to CREB3L2. Testing of FUS locus rearrangement should be concomitant with histologic evaluation, and positive results may support the diagnosis of LGFMS.

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

A neoplastic clone is detected when the percent of cells with an abnormality exceeds the normal cutoff for the FUS probe set.

 

A positive result is consistent with the diagnosis of low-grade fibromyxoid sarcoma (LGFMS).

 

A negative result suggests that a FUS gene rearrangement is not present, but does not exclude the diagnosis of LGFMS.

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

This test is not approved by the FDA and it is best used as an adjunct to existing clinical and pathologic information.

 

Fixatives other than formalin (eg, Prefer, Bouin's) may not be successful for FISH assays. Although FISH testing will not be rejected due to nonformalin fixation, results may be compromised.

 

Paraffin-embedded tissues that have been decalcified are generally unsuccessful for FISH analysis. The pathologist reviewing the hematoxylin and eosin-stained slide may find it necessary to cancel testing.

Supportive Data

FISH analysis was performed on 47 formalin-fixed, paraffin-embedded tissue samples including 13 low-grade fibromyxoid sarcoma (LGFMS) tumors, 8 histologic mimics of LGFMS, and 26 noncancerous control specimens. The normal controls were used to generate a normal cutoff for this assay. Rearrangement of FUS was identified in 8 of 13 (62%) LGFMS specimens.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Who Health Organization Classification of Tumors. Pathology and Genetics of Tumours of Soft Tissue and Bone. Low grade myofibroblastic sarcoma. Edited by CDM Fletcher, KK Unni, F Mertens. Lyon, IARC Press, 2002, pp 104-105

2. Downs-Kelly E, Goldblum JR, Patel RM, et al: The utility of fluorescence in situ hybridization (FISH) in the diagnosis of myxoid soft tissue neoplasms. Am J Surg Pathol 2008;32:8-13

3. Mertens F, Fletcher CD, Antonescu CR, et. Al: Clinicopathologic and molecular genetic characterization of low-grade fibromyxoid sarcoma, and cloning of a novel FUS/CREB3L1 fusion gene. Lab Invest 2005;85:408-415

4. Vernon SE, Bejarano PA: Low-grade fibromyxoid sarcoma: a brief review. Arch Pathol Lab Med 2006;130:1358-1360