Pleuropulmonary blastoma and DICER1-related disorders

DICER1 mutations are implicated in a broad range of tumors: pleuropulmonary blastoma (PPB), cystic nephroma (CN), ovarian Sertoli-Leydig cell tumors (SLCTs), ciliary body medulloepithelioma (CBME) and other tumor types.

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Test Code: 5260 Test Name: DICER1 seq and del/dup TAT 14-21 days Gene: 1
Test Code: 5262 Test Name: DICER1 specific site analysis TAT 7-14 days Gene: 1

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Why Is This Important?

  1. Option to modify age, frequency, and type of cancer screening 
  2. May aid in a clinical diagnosis, particularly of a pleuropulmonary blastoma 
  3. Identify at-risk family members

When To Consider Testing

DICER1 genetic testing may be considered for patients who are suspected to have one or more of the following:

  • Pleuropulmonary blastoma (PPB)
  • Cystic nephroma
  • Ovarian Sertoli-Ledig cell tumors 
  • Family history of a known DICER1 mutation

 

Mutation Detection Rate

50-75% of patients with pleuropulmonary blastoma (PPB) have a detectable mutation in the DICER1 gene (clinical sensitivity).

Ambry DICER1 analysis (gene sequencing only) can detect >99.9% of described mutations in the gene, when present (analytic sensitivity).

Test Description

DICER1 coding exons 1-26 and well into the 5’ and 3’ ends of all the introns and untranslated regions are analyzed by sequencing. Gross deletion/duplication analysis determines gene copy number for coding exons 1-26. Clinically significant intronic findings beyond 5 base pairs are always reported. Intronic variants of unknown or unlikely clinical significance are not reported beyond 5 base pairs from the splice junction. Genomic deoxyribonucleic acid (gDNA) is isolated from the patient’s specimen using standardized methodology and quantified. Sequence enrichment of the targeted coding exons and adjacent intronic nucleotides is carried out by a bait-capture methodology, using long biotinylated oligonucleotide probes followed by polymerase chain reaction (PCR) and next generation sequencing (NGS). Sanger sequencing is performed for any regions missing or with insufficient read depth coverage for reliable heterozygous variant detection. Reportable small insertions and deletions, potentially homozygous variants, variants in regions complicated by pseudogene interference, and single nucleotide variant calls not satisfying 100x depth of coverage and 40% het ratio thresholds are verified by Sanger sequencing.1  Gross deletion/duplication analysis of DICER1 using read-depth from NGS data is also performed. Any copy number changes detected by NGS are confirmed by targeted chromosomal microarray and/or multiplex ligation-dependent probe amplification (MLPA).

 

1.Mu W, et al. Sanger confirmation is required to achieve optimal sensitivity and specificity in next-generation sequencing panel testing. J Mol Diagn. 2016. 18(6):923-932.

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