Melanoma

Primary Author Wallander, Michelle, PhD.

Key Points

Disseminated melanoma is generally unresponsive to traditional chemotherapy and/or radiotherapy. With the advent of targeted therapy, molecular testing in melanoma has gained importance.

  • Mutations by biology and targeted therapy

Mutation

Biology

Targeted Therapy

Comments

BRAF gene

ARUP Test

BRAF Codon 600 Mutation Detection by Pyrosequencing 2002498

  • BRAF is a protein involved in the MAPK pathway, which includes BRAF/MEK/ERK signaling
  • Activates pathway, mediates growth signaling, links with factor receptors (eg, tyrosine kinases), leading to cell growth and depression of immune regulation of cancer cells
  • >80% mutations substitute glutamic acid for valine at codon 600, resulting in V600E mutation
    • Other mutations – V600K, V600R, V600D

BRAF V600E inhibitors – vemurafenib (PLX4032) and dabrafenib (GSK2118436)

MEK inhibitors in phase I and II trials – AZD6244, GSK112012

  • 40-50% of melanomas (Solas, 2013)
  • Molecular genetic testing required if therapy directed at BRAF V600E mutation is being considered
  • Associated with melanomas of intermittent acute sun-damaged skin, younger age (<55 yrs), and poorer prognosis compared to BRAF and NRAS wild type melanomas
  • Resistance develops in all patients
    • Resistance to BRAF inhibitors develops downstream, not at the initial mutation site
  • Combining BRAF with MEK inhibition may improve outcome

RAS family of genes

(NRAS, KRAS, HRAS)

ARUP Test

NRAS Mutation Detection by Pyrosequencing   2003123

  • NRAS is a protein involved in the MAPK pathway
  • Most mutations are in NRAS gene
  • Mutation leads to defective GTPase activity with uncontrolled cell proliferation
  • Most common mutations are located in codons 12, 13, and 61
  • Mutation is generally mutually exclusive of BRAF mutation

None available yet

Clinical trials combining BRAF with MEK, ATK, and  PI3K inhibitors

  • 15-20% of melanomas (Solus, 2013)
  • Associated with thicker tumors, higher mitotic rate, and worse prognosis than BRAF mutation or BRAF/NRAS wild type

KIT gene

ARUP Test

KIT Mutations, Melanoma 2002695

  • KIT gene encodes for type III transmembrane receptor tyrosine kinase, which is involved in regulation of MAPK and PI3K pathways
  • Mutations function as oncogene
  • Exons 9, 11, 13, 14, 17, 18
  • Most common mutations are located in exon 11

Tyrosine kinase inhibitors (TKIs) – imatinib; dasatinib in clinical trials

  • Rate of occurrence dependent on type of melanoma
    • Most common in acral lentiginous, sun-damaged skin or mucosal melanomas
  • Molecular genetic testing should be performed if TKIs are being considered
    • KIT IHC staining does not predict mutation status or sensitivity to TKIs
    • Exons 11, 13 most likely to have response to TKIs
  • Resistance develops in most patients with a secondary mutation in KIT gene

PDGFRA gene

ARUP Test

KIT Mutations, Melanoma 2002695

  • PDGFRA gene provides instructions to create platelet-derived growth factor
  • Rare in melanoma
  • Most common mutations in exons 12, 14, 18

TKIs

  • Best response for V658A
  • Better response for crenolanib compared to imatinib
  • Exons 12, 14, 18 in PDGFRA gene may be associated with TKI sensitivity
PTEN gene
  • Functions as  lipid phosphatase regulating PI3K/AKT pathways
  • Mutation causes high-level activation of pathway with unregulated cell growth and proliferation
  • Mutation is generally mutually exclusive of NRAS  gene mutations, but usually inclusive for BRAF gene mutations
Multiple classes of inhibitors in phase I and II trials – PI3K, AKT, mTORC1, dual PI3K/mTOR inhibitors 

Diagnosis

Indications for Testing

  • Atypical melanocytic lesion (mole) requires histologic evaluation

Histology

  • Gold standard for diagnosis
    • Immunohistochemistry may be required to distinguish poorly differentiated lesions of carcinoma, sarcoma, or lymphoma (B-cell or T-cell) from melanoma
    • Stains to consider include cytokeratin 8,18 low molecular weight (CAM 5.2); melanoma antibody, HMB45; Ki-67 (Mib-1); melan A; p21 (Waf1/Cip 1); S-100 protein; and vimentin
  • Architectural and cytologic features of biopsy are interpreted in the context of clinical information
    • Architecture – large, asymmetrical, poorly circumscribed lesion; pagetoid spread of melanocytes; effaced rete ridges and underlying dermal architecture; perineural invasion
    • Cytology – large nuclei with prominent nucleoli; atypical mitosis (especially in dermis); lack of melanocyte maturation in deep portion of lesion
  • Metaplastic differentiation (nonmelanocytic cells or tissues) may be identified that may not be melanoma
  • Molecular – refer to Key Points

Imaging Studies

  • Routine cross-sectional imaging (CT, PET, MRI) is not recommended  in patients with localized melanoma due to low yield

Genetic Testing

  • Should be offered to individuals with
    • Three or more diagnoses of melanoma and/or pancreatic cancer in first- or second-degree relative
    • Three or more synchronous or metachronous primary melanomas
    • Synchronous or metachronous melanoma and pancreatic cancer

Prognosis

  • Depth of tumor invasion – used to determine prognosis
    • Breslow thickness – most important factor contributing to T status in tumor, nodes and metastasis staging
      • Measured from top of epidermal granular cell layer to deepest malignant melanocyte
      • 5-year survival rate – 95.3% with Breslow thickness ≤1.0 mm (corresponds to T1 lesion), 45.1% with Breslow thickness >4.0 mm
    • Clark level – important in T1 lesions (<1 mm thick) (corresponds to 95% or better survival)
      • Clark I – melanoma in situ; does not cross basement membrane
      • Clark II – invasion of papillary dermis
      • Clark III – expansion of papillary dermis
      • Clark IV – invasion of reticular dermis
      • Clark V – invasion of subcutaneous fat
  • Additional histologic features used to determine prognosis
    • Involvement of regional lymph nodes (regional nodal dissection or sentinel node testing)
    • Metastasis
    • Growth phase
    • Mitotic count
    • Regression
    • Ulceration
  • Additional serum testing
    • Lactate dehydrogenase – prognostic factor in late-stage melanoma
      • Elevated levels may indicate metastasis
    • S-100B, serum – elevated level associated with poor prognosis

Differential Diagnosis

  • Clinical – melanocytic nevi
  • Histologic
    • Well-differentiated – melanocytic nevi
    • Poorly differentiated – carcinoma, sarcoma, lymphoma (T-cell, B-cell)

Screening

  • The American Academy of Dermatology (AAD) and American Cancer Society (ACS) recommend regular skin exams in all patients
    • The U.S. Preventive Services Task Force finds insufficient evidence to recommend regular skin exams

Monitoring

  • The National Comprehensive Cancer Network (NCCN) recommends skin examination at least once per year for life for melanoma patients (including those with stage 0, in situ melanoma)
    • Patients with stage IA-IIA melanoma, no evidence of disease
      • Comprehensive exam every 3-12 months for five years and annually thereafter as clinically indicated
    • Patients with stage IIB-IV melanoma, no evidence of disease
      • Comprehensive exam every 3-6 months for two years, then every 3-12 months for three years and annually thereafter as clinically indicated
    • Although not recommended at baseline, x-ray, CT/MRI, and/or PET/CT every 6-12 months can be considered to screen for recurrent or metastatic disease at discretion of physician
      • Most recurrences manifest within first five years – routine imaging not recommended beyond this period
  • S-100B, serum
    • Rising concentrations after treatment indicate disease recurrence

Clinical Background

Melanoma is a malignancy of the melanocytes. This disease is experiencing a rising incidence worldwide, ranking second to adult leukemia in loss of years of potential life per death.

Epidemiology

  • Incidence – 18/100,000
    • ~77,000 new melanomas and >9,700 deaths in U.S. annually (American Cancer Society, 2014)
    • Tripled over the last 20 years
    • Highest incidence worldwide is in Australia
  • Age – median is 57 years; rare in children
  • Sex – M>F, 1.5:1
  • Ethnic – 10-fold increased incidence in Caucasians
    • Acral lentiginous melanoma has equal distribution across all ethnic groups

Inheritance

  • Gene mutations associated with hereditary melanoma

    Gene Symbol*

    Germline Mutations Increase Risk for the Following Cancer Types

    Percentage of Hereditary Melanoma** Attributed to Gene

    BAP1

    Mesothelioma; melanoma of the eye

    Rare

    CDK4

    Melanoma

    2%

    CDKN2A

    Melanoma; pancreatic

    20-40%

    PTEN

    Thyroid; breast; renal; colorectal; endometrial; melanoma

    Rare

    RB1

    Retinoblastoma; pinealoblastoma; sarcomas; melanoma

    Rare

    TP53

    Li-Fraumeni syndrome; sarcoma; leukemia; breast; brain; adrenocortical; hepatocellular; melanoma

    Rare

    *All genes have autosomal dominant inheritance

    **~5-10% of melanomas are hereditary

Classification

  • Superficial spreading melanoma (~70%)
  • Nodular melanoma (10-15%)
  • Lentigo maligna melanoma (10%)
  • Acral lentiginous melanoma (~5%)
  • Mucosal lentiginous melanoma (3%)

Risk Factors

  • Sunlight – sunburns in childhood, intermittent UV exposure associated with higher risk
  • Blue or green eyes; red or blond hair
  • Melanocytic nevus – increased risk by number and size of nevi
  • Family history – 2-fold risk if first-degree relative had melanoma
    • Clustering of melanoma in familial retinoblastoma and Li-Fraumeni syndrome
    • Increased risk of familial melanoma in the presence of family history of pancreatic cancer or astrocytoma
  • Immunosuppression

Genetics

  • BRAF gene mutations
    • 40-60% of melanomas
    • Most common in cutaneous melanomas derived from intermittent sun-exposed skin
  • KIT gene mutations
    • As many as 15% of melanomas
    • Most common in mucosal and acral lentiginous, sun-damaged skin; small presence in sun-damaged melanomas
    • Most common mutations located at exons 9,11,13, and 17
    • Predicted to respond favorably to the tyrosine kinase inhibitor imatinib
  • NRAS gene mutations
    • 15-20% of melanomas
    • Associated with thicker tumors, high mitotic rate, and worse prognosis than mutations in BRAF gene or wild type BRAF/NRAS genes
    • Most common mutations located in codons 12,13, and 61
    • Generally mutually exclusive of BRAF gene mutations
  • PDGFRA gene mutations
    • Rare
    • Usually exons 12, 14, 18 (exons 12 and 14 more favorable prognosis)
  • PTEN gene mutations
    • Generally mutually exclusive of NRAS gene mutations, but usually inclusive for BRAF gene mutations

Clinical Presentation

  • 82-85% of melanoma patients present with localized disease; 10-30% present with regional disease; 2-5% with distant metastatic disease
  • Nevus with Asymmetry, Border irregularity, Color variation, Diameter >6 mm and Evolving changes (ABCDE criteria)
  • Head and neck most common sites
  • Ulceration, pigment loss
  • Rare sites – eye (iris, ciliochoroidal), mucosa, unknown primary
  • Mortality rates have plateaued in recent years (attributed to early diagnosis)

Pediatrics

Clinical Background

Epidemiology

  • Incidence – 300-425 cases annually in the U.S. (NCI, 2006)
  • Age – 15-19 years most common
  • Sex – M>F (minimal)

Risk Factors

  • Family history – 2-fold risk if first-degree relative had melanoma
    • Clustering of melanoma in familial retinoblastoma and Li-Fraumeni syndrome
    • Increased risk of familial melanoma in the presence of family history of pancreatic cancer or astrocytoma
  • History of severe sunburns (>3 before 20 years)
  • Xeroderma pigmentosa
  • Immunosuppression
  • Dysplastic nevi (3- to 6-fold increased risk)

Clinical Presentation

  • Lesions frequently amelanotic or nodular
  • ABCDE criteria (Asymmetry, Border irregularity, Color variation, Diameter >6 mm, and Evolving changes) less reliable than in adults

Diagnosis

Indications for Testing

  • Refer to Diagnosis tab

Laboratory Testing

  • Refer to Diagnosis tab

Histology

  • Congenital nevus has slightly different histologic appearance
  • Refer to Histology section in Diagnosis tab

Imaging Studies

  • Refer to Diagnosis tab

Differential Diagnosis

  • Spitz nevus
  • Blue nevus
  • Congenital nevus

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
BRAF Codon 600 Mutation Detection by Pyrosequencing 2002498
Method: Polymerase Chain Reaction/Pyrosequencing

Detect activating BRAF mutations associated with anti-EGFR therapy resistance

Detects activating mutations in KIT gene (exons 9. 11. 13, 14, 17, 18) and PDGFRA gene (exons 12, 14, 18)

Analytical sensitivity/specificity – 99%

Limit of detection – 10% mutant alleles

Oncogenic mutations outside of codon 600 will not be detected

 
KIT Mutations, Melanoma 2002695
Method: Polymerase Chain Reaction/Sequencing

Provide prognostic and predictive information for  kinase inhibitor (TKI) therapy planning

Analytical sensitivity – 25% mutant alleles (50% tumor)

Mutations outside of targeted exons will not be detected

 
NRAS Mutation Detection by Pyrosequencing 2003123
Method: Polymerase Chain Reaction/Pyrosequencing
Screen for tumors that may respond to therapy targeted to downstream genes in the MAPK signalling pathway

Limit of detection – 10% mutant alleles

Oncogenic mutations outside of codons 12, 13, and 61 will not be detected

Presence or absence of mutations does not guarantee a positive response to anti-EGFR therapies

 
Cytokeratin 8,18 Low Molecular Weight (CAM 5.2) by Immunohistochemistry 2003493
Method: Immunohistochemistry

Aid in histologic diagnosis of melanoma

Stained and returned to client pathologist; consultation available if needed

   
Melanoma Antibody, HMB45 by Immunohistochemistry 2003935
Method: Immunohistochemistry

Aid in histologic diagnosis of melanoma

Stained and returned to client pathologist; consultation available if needed

   
Ki-67 with Interpretation by Immunohistochemistry 2007182
Method: Immunohistochemistry

Aid in histologic diagnosis of melanoma

Stained and resulted by ARUP

   
Melan A by Immunohistochemistry 2003996
Method: Immunohistochemistry

Aid in histologic diagnosis of melanoma

Stained and returned to client pathologist; consultation available if needed

   
S-100 Protein by Immunohistochemistry 2004127
Method: Immunohistochemistry

Aid in histologic diagnosis of melanoma

Stained and returned to client pathologist; consultation available if needed

   
Vimentin by Immunohistochemistry 2004181
Method: Immunohistochemistry

Aid in histologic diagnosis of melanoma

Stained and returned to client pathologist; consultation available if needed

   
p21 (Waf1/Cip 1) by Immunohistochemistry 2004067
Method: Immunohistochemistry

Aid in histologic diagnosis of melanoma

Stained and returned to client pathologist; consultation available if needed

   
BRAF V600E by Immunohistochemistry 2008710
Method: Immunohistochemistry

Aid in histologic diagnosis of melanoma

Stained and returned to client pathologist; consultation available if needed

   
Lactate Dehydrogenase, Serum or Plasma 0020006
Method: Quantitative Enzymatic

Monitor treatment and determine prognosis of patients with malignant melanoma

Not used for diagnosis

 
S-100B Protein, Serum 2001766
Method: Quantitative Enzyme-Linked Immunosorbent Assay

Monitor treatment and determine prognosis of patients with malignant melanoma

Not used for diagnosis; S-100B is not specific for malignant melanoma; increased serum concentrations are found in patients with liver and renal injury, inflammation, infection, and brain injury

 
Melanoma Hereditary Cancer Panel, Sequencing and Deletion/Duplication, 6 Genes  2010209
Method: Massive Parallel Sequencing/Exonic Oligonucleotide-based CGH Microarray

Confirm suspected hereditary melanoma in individual with personal or family history of melanoma

Preferred test for individuals at high risk for hereditary melanoma

Genes included – BAP1, CDK4, CDKN2A, PTEN, RB1, TP53

Analytical sensitivity/specificity – 99%

Diagnostic errors can occur due to rare sequence variations

Not determined or evaluated

  • Mutations in genes not included on panel
  • Deep intronic and regulatory region mutations
  • Breakpoints for large deletions/duplications
  • Large deletions/duplications in exon 1 of BAP1 gene
  • Exon 8 of PTEN gene

Lack of a detectable gene mutation does not exclude a diagnosis of hereditary melanoma

 Not all predisposing genes are analyzed

Individuals with hematological malignancy and/or a previous allogenic bone marrow transplant should not undergo molecular genetic testing on peripheral blood specimen

 
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
BRAF V600E Mutation Detection by Allele-Specific PCR, Fine Needle Aspirate 2006516
Method: Polymerase Chain Reaction

Diagnosis, prognosis, and therapeutic decisions in a variety of tumors

Assess for responsiveness to BRAF inhibitor therapy

For tissue block or formalin-fixed, paraffin-embedded (FFPE) cell blocks prepared from FNA, BRAF Codon 600 Mutation Detection by Pyrosequencing may be used

Solid Tumor Mutation Panel by Next Generation Sequencing 2007991
Method: Massively Parallel Sequencing

Prognosis/treatment of individuals with solid tumor cancers at initial diagnosis or with refractory disease

48-gene panel assay for detection of mutations, including KRAS, EGFR, BRAF, and ERBB2 genes