Inflammatory Myofibroblastic Tumors (IMT), 2p23 Rearrangement, FISH, Tissue
Supporting the diagnosis of inflammatory myofibroblastic tumor 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
Inflammatory myofibroblastic tumor (IMT) is a distinctive lesion composed of myofibroblastic spindle cells accompanied by an inflammatory infiltrate of plasma cells, lymphocytes, and eosinophils which occur primarily in the soft tissue and viscera of children and young adults. They may arise in any anatomical site including lung, soft tissue, retroperitoneum, and bladder.
The genetic mechanisms underlying IMT pathogenesis are only partially known, but cytogenetic analyses have disclosed chromosomal rearrangements involving the ALK gene at 2p23. Recently, studies support that identification of ALK gene rearrangement is useful to differentiate IMTs from other spindle cell neoplasms of soft tissue and viscera.
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 interpretive report will be provided.
A neoplastic clone is detected when the percent of cells with an abnormality exceeds the normal cutoff for the ALK probe set.
A positive result is consistent with a subset of inflammatory myofibroblastic tumor (IMT).
A negative result suggests that a ALK gene rearrangement is not present but does not exclude the diagnosis of IMT.
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 non-formalin 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.
FISH analysis was performed on 26 inflammatory myofibroblastic tumors (IMT) (21 bladder, 5 soft tissue), 33 non-IMT spindle tumors, and 50 noncancerous control specimens (25 bladder and 25 soft tissue). The normal controls were used to generate a normal cutoff for this assay. Rearrangement of ALK was identified in 18 of 26 IMT specimens. Immunohistochemical staining confirmed these to be negative for ALK-1. The remaining spindle cell tumors were found to be negative for ALK rearrangement and ALK-1 staining.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Coffin CM, Fletcher JA: Chapter II: Inflammatory myofibroblastic tumour. In World Health Organization Classification of Tumors. Pathology and Genetics of Tumours of Soft Tissue and Bone. Edited by CDM Fletcher, KK Unni, F Mertens. Lyon, IARC Press, 2002, pp 91-93
2. Sukov WR, Cheville JC, Carlson AW: Utility of ALK-1 protein expression and ALK rearrangements in distinguishing inflammatory myofibroblastic tumor from malignant spindle cell lesions of the urinary bladder. Mod Pathol 2007 May;20(5):592-603
3. Tsuzuki T, Magi-Galluzzi C, Epstein JI: ALK-1 expression in inflammatory myofibroblastic tumor of the urinary bladder. Am J Surg Pathol 2004;28:1609-1614
4. Li XQ, Hisaoka M, Shi DR: Expression of anaplastic lymphoma kinase in soft tissue tumors: an immunohistochemical and molecular study of 249 cases. Hum Pathol 2004 Jun;35(6):711-721
5. Griffin CA, Hawkins AL, Dvorak C, et al: Recurrent involvement of 2p23 in inflammatory myofibroblastic tumours. Cancer Res 1999;59:2776-2780