Desmoid tumor laboratory tests

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sara Mohsin, M.D.[2]

Overview

Immunohistochemical staining of spindle cells of desmoid tumors are positive for nuclear beta-catenin, vimentin, alpha smooth muscle actin, muscle actin and negative for desmin, cytokeratins, and S-100. Antibodies like smooth muscle actin, desmin and KIT may be helpful in distinguishing desmoid tumors from other tumors. In addition, APC germline mutations may be performed in patients with sporadic desmoid tumors with no clinical or famililal signs of FAP but having a family history of colorectal carcinoma in at least one family member.

Laboratory tests

• The molecular testing can be performed in general by performing a variety of following methods:
  • In situ hybridization technique, such as fluorescence in situ hybridization (FISH)
  • Immunohistochemistry (IHC)
  • Next-generation sequencing (NGS)
  • Polymerase chain reaction (PCR)
  • Comparative genomic hybridization (CGH)
  • Karyotyping including spectral karyotyping
  • mRNA analysis
  • Tissue microarrays (TMAs)
  • Southern blot test
  • Northern blot test
  • Western blot test
  • Eastern blot test

Clinical indications for performing molecular testing

• Molecular testing for Desmoid Tumor is done in order to:
  • Assist (and in some cases, confirm) the initial diagnosis of desmoid tumor
  • Distinguish other tumors/conditions that have similar histological features, when examined by a pathologist under the microscope
  • Help in determining treatment options
  • Confirm recurrence of the tumor: Tumor recurrence can either be at the original tumor site, or at a distant location (away from the initial site)

Significance of Molecular Testing

• Molecular testing in desmoid tumor has following significance:
  • Presence of a positive test result helps aid, and in some cases, confirm the diagnosis of desmoid tumor
  • Result can help to exclude other tumors having similar histological features
  • It can help in determining the prognosis of the patient
  • Test results may help in making treatment decisions in some cases

Characteristic features of desmoid tumors on immunohistochemistry and relevant antibodies

Other diagnostic tests	Associated characteristics features
Immunohistochemistry (aids histologic diagnosis)	Spindle cells on immunohistochemical stains show the following features: Positive for: Nuclear beta-catenin (regardless of the site, 90% of desmoids show nuclear reactivity, relatively high specificity) Vimentin Alpha smooth muscle actin Muscle actin Negative for: Desmin Cytokeratins S-100
Antibodies	In order to distinguish desmoid tumors from other tumors, following antibodies are often examined: Smooth muscle actin Desmin KIT
APC germline mutational analysis	Sporadic desmoid tumor patients with no clinical or familial signs of familial adenomatous polyposis (FAP) but having a family history of colorectal carcinoma in at least one family member