Multiple Myeloma by FISH

Detect genetic abnormalities predictive of outcome in individuals with MM

Multiple myeloma (MM) is a plasma cell dyscrasia that can evolve from a premalignant monoclonal gammopathy. Prognosis often depends on the presence or absence of particular genetic markers. Fluorescence in situ hybridization (FISH) testing for relevant markers should be performed upon diagnosis and in low-risk individuals at time of relapse to aid in risk stratification. 

Test Description

Plasma cells are isolated from a bone marrow (BM) aspirate using CD138+ microbeads. CD138+ cells (plasma cells) are then analyzed by FISH using specific probes for the following:

  • CCND1/IGH fusion t(11;14)
  • CKS1B (1q gain)
  • IGH rearrangement (14q32)
  • ASS1 (+9)
  • PML (+15)
  • TP53 (17p deletion)

If IGH rearrangement detected does not involve CCND1, additional probes are added:

  • FGFR3/IGH fusion t(4;14)
  • MAF/IGH fusion t(14;16)

Disease Overview

Incidence

1.8% of all cancers in the U.S. 

Age of Onset

Most frequently diagnosed between ages 65 and 74 years (median age 69 years) 

Symptoms

Presenting clinical features include symptoms of  :

  • Hypercalcemia
  • Impaired renal function
  • Anemia
  • Bone disease (lesions)

FISH Testing and Prognostic Issues

Abnormalities are detected by conventional cytogenetics in ~30% of MMs. FISH testing increases this number to >90%.  Cytogenetic abnormalities affect the prognosis of patients with MM. Because most genetic subtypes in MM are primary, ploidy state, IGH translocation, and genetic status need only be assessed once at diagnosis.  However, repeat testing is justified in cases of gain/amplification of CKS1B (1q21) and deletion of TP53 (17p13), as these markers occur in disease progression and confer a worse ​prognosis.  

Genetic Markers and Resulting Prognostic Issues
Markers Characteristics and Prognostic Value Recurrent Testing 
Primary Cytogenetic Abnormalities

Hyperdiploidy​

Usually gains (trisomies) of three or more odd-numbered chromosomes (3, 5, 7, 9, 11, 15, 19, 21) 

Presence: 40-60% of MM  

Standard risk 

Infrequently occurs with IGH translocations  

Panel tests most commonly gained chromosomes (9, 11, 15)

Test only once

14q32 (IGH) rearrangement

7 major oncogenes involved: 11q13 [CCND1], 16q23 [MAF], 4p16 [FGFR3/MMSET], 6p21 [CCND3], 20q11 [MAFB], 8q24 [MAFA], 12p13 [CCND2] 

Main translocations are t(11;14), t(4;14), t(14;16), and t(14;20) 

Presence: 45-70% of MM 

Prognosis varies depending on translocation partner:

  • t(11;14)(q13;q14) confers standard risk
  • t(4;14), t(14;16), and t(14;20) generally associated with poor prognosis

IGH translocations are generally mutually exclusive and associated with nonhyperdiploidy​

Test only once

t(4;14)(p16;q32) IGH-FGFR3/MMSET

Presence: 5% of MM  

High to intermediate risk  

Detectable only by FISH (cytogenetically cryptic)

Test only once

t(11;14)(q13;q32) IGH-CCND1

Presence: 15% of MM 

Standard risk  

Test only once

t(14;16)(q32;q23) IGH-MAF

Presence: 5% of MM 

High risk  

Test only once

Secondary Cytogenetic Abnormalities

Gain/amplification of 1q21 (CKS1B)

Presence: 30-70% of MM  

Presence higher in disease progression

High risk

May be observed in hypodiploid, hyperdiploid, and IGH translocation-positive MM

Confers a poor prognosis in all subtypes

Repeat testing justified

Deletion 17p (TP53)

Presence: 5-10% of MM  

Presence higher in disease progression

High risk  

May be observed in hypodiploid, hyperdiploid, and IGH translocation-positive MM

Confers a poor prognosis in all subtypes

Repeat testing justified

Test Interpretation

Analytical Sensitivity/Specificity

>95%

Results

  • Abnormal: gain/loss/rearrangement/translocation detected; percentage of cells affected (out of 200) reported
  • Normal: no evidence of gains, deletions, rearrangements, or translocations of loci tested

Limitations

Only detects aberrations specific to probes used

    References