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Molecular Testing for Melanotic Schwannoma

Last updated March 10, 2017

Molecular Testing for Melanotic Schwannoma is a genetic test that is helpful in aiding a diagnosis of melanotic schwannoma.

What are other Names of this Test? (Equivalent Terms)

  • Gene Mutation Analysis for Melanotic Schwannoma
  • Test for Molecular Diagnosis of Melanotic Schwannoma

What is Molecular Testing for Melanotic Schwannoma? (Background Information)

  • Molecular Testing for Melanotic Schwannoma is a genetic test that is helpful in aiding a diagnosis of melanotic schwannoma. The lab test results may also be subsequently useful in taking appropriate treatment decisions
  • Melanotic schwannoma is a rare tumor of the soft tissue involving the nerves of the body. It is called so, because the Schwann cells (a type of nerve cells) produce melanin pigment. The tumor is mostly found in young adults
  • About half of the cases occur in individuals with Carney complex, which is an autosomal dominant genetic condition. Carney complex is characterized by the presence of multiple tumors, such as myxomas, schwannomas, and pigmented skin conditions
  • The signs and symptoms of melanotic schwannomas are linked to the tumor site. Although most tumors are benign, some may be malignant. The malignant melanotic schwannomas may metastasize to various body organs (such as lung and brain)

The cause of melanotic schwannoma is due to genetic mutations.

  • Currently, studies indicate defects in the following gene: CNC2
  • Additionally, the following chromosomal aberration is noted:
    • Abnormalities in chromosome 2 is observed with additions/deletions in 2p16 region
    • Such changes are seen irrespective of whether the tumors are associated with Carney complex or not

The above genetic abnormalities can be detected using molecular studies, which may play a significant role in identifying the tumor type, and in some cases, helping the healthcare provider take appropriate treatment decisions.

The molecular testing, in general, can be performed using a variety of methods. Some of these methods include:

  • 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

The methodology used for melanotic schwannoma may vary from one laboratory to another. 

Note: Molecular testing has limitations due to the molecular method and genetic mutational abnormalities being tested. This can affect the results on a case-by-case basis. Consultation with your healthcare provider will help in determining the right test and right molecular method, based on individual circumstances.

What are the Clinical Indications for performing the Molecular Testing for Melanotic Schwannoma Test?

Molecular Testing for Melanotic Schwannoma is undertaken in the following situations: 

  • To assist (and in some cases, confirm) the initial diagnosis of melanotic schwannoma
  • To distinguish other tumors/conditions that have similar histological features, when examined by a pathologist under the microscope
  • To help in determining treatment options
  • To 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)

How is the Specimen Collected for Molecular Testing for Melanotic Schwannoma?

Following is the specimen collection process for Molecular Testing for Melanotic Schwannoma:

The specimen sample requirements may vary from lab to lab. Hence, it is important to contact the testing lab for exact specimen requirements, before initiating the testing process.

  • Sample on which the test is performed may include:
    • Fresh tumor tissue during biopsy
    • Formalin-fixed paraffin-embedded solid tumor tissue (FFPE tumor tissue), often referred to as paraffin block of the tumor
    • Unstained tissue slides
  • Process of obtaining the sample: As outlined by the laboratory testing facility
  • Preparation required: As outlined by the laboratory testing facility


  • In some cases, a different source of specimen (such as peripheral blood, bone marrow biopsy specimen, or other body fluids) may be acceptable to the laboratory performing the test
  • Occasionally, additional samples may be required to either repeat the test or to perform follow-up testing
  • Depending on the location of testing, it may take up to 2 weeks’ turnaround time, to obtain the test results
  • Many hospitals preserve the paraffin blocks for at least 7 years. In general, older paraffin blocks (over 5 years) may affect the detection of specific mutations, due to degradation of the tumor specimen over time

Cost of Molecular Testing for Melanotic Schwannoma:

  • The cost of the test procedure depends on a variety of factors, such as the type of your health insurance, annual deductibles, co-pay requirements, out-of-network and in-network of your healthcare providers and healthcare facilities
  • In many cases, an estimate may be provided before the test is conducted. The final amount may depend upon the findings during the test procedure and post-operative care that is necessary (if any)

What is the Significance of the Molecular Testing for Melanotic Schwannoma Result?

The significance of Molecular Testing for Melanotic Schwannoma is explained:

  • Presence of a positive test result helps aid, and in some cases, confirm the diagnosis of melanotic schwannoma
  • The result can help exclude other tumors with similar histological features
  • It can help determine the prognosis of the patient
  • In some cases, the test results may help in taking treatment decisions

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Many laboratories may not have the capability to perform this test. Only highly-specialized labs with advanced facilities and testing procedures may perform this test
  • Additional mutations are still being discovered in many of these tumors. This may further contribute towards tumor diagnosis and treatment. Please consult with your healthcare provider for any information updates

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider of the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

What are some Useful Resources for Additional Information?

Please visit our Laboratory Procedures Center for more physician-approved health information:


References and Information Sources used for the Article:

https://ghr.nlm.nih.gov/primer/testing/genetictesting (accessed on 03/07/2017)

https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5806a1.htm (accessed on 03/07/2017)

http://www.nature.com/gim/journal/v10/n5/full/gim200852a.html (accessed on 03/07/2017)

http://pediatrics.aappublications.org/content/106/6/1494 (accessed on 03/07/2017)

http://www.jto.org/article/S1556-0864(16)32820-9/fulltext (accessed on 03/07/2017)

http://www.jto.org/ (accessed on 03/07/2017)

https://www.ncbi.nlm.nih.gov/pubmed/20301463 (accessed on 03/07/2017)

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Torres-Mora, J., Dry, S., Li, X., Binder, S., Amin, M., & Folpe, A. L. (2014). Malignant melanotic schwannian tumor: a clinicopathologic, immunohistochemical, and gene expression profiling study of 40 cases, with a proposal for the reclassification of “melanotic schwannoma”. The American journal of surgical pathology, 38(1), 94-105.

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Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: March 10, 2017
Last updated: March 10, 2017