BRAF V600E Mutation Positive Malignant Melanoma | Molecular Pathology Laboratory Network, Inc.

BRAF V600E Mutation Positive Malignant Melanoma

A recently published phase 3 clinical trial demonstrates that a novel melanoma therapy targeted to the BRAF V600E gene mutation has significant therapeutic efficacy against BRAF V600E mutated melanomas. The BRAF V600E mutation is present in 30-60% of cutaneous melanomas.

Vemurafenib, a drug with specific inhibitory activity against the BRAF V600E mutated kinase, demonstrates superior overall and progression-free survival compared to dacarbazine in patients with previously untreated, metastatic BRAF V600E mutation-positive melanoma.

Oncologists can now consider vemurafenib therapy for high stage melanoma patients who are positive for BRAF V600E gene mutation.

By coincidence, a separate unrelated publication released ahead of print at the same time by the NEJM describes successful treatment of metastatic melanoma with a different, novel therapy, ipilimunab, a monoclonal antibody drug that activates anti-tumor T cell activity by blocking cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4). And thirdly, a June issue of JAMA reports successful use of Gleevec® in treating c-kit amplified malignant melanoma. Among a subset of patients with c-kit amplified melanomas, 16% had a significant response to Gleevec.

These are striking therapeutic developments. Monoclonal anti-CTLA-4 therapy is arguably a modern extrapolation of longstanding attempts to treat melanoma by immune modulation. In contrast, vemurafenib and Gleevec represent targeted therapies directed towards measurable melanoma genotypes, those containing the BRAF V600E mutation or c-kit amplification, both of which require laboratory testing for drug eligibility.

BRAF V600E gene mutation
Melanocytic Markers by IHC

History
Microscopy
Special Studies
References

A 61 year-old female with known history of malignant melanoma developed a right pleural effusion and underwent pleural biopsy.

Routine histologic sections demonstrate sheets of mitotically active, loosely cohesive malignant cells with open chromatin, single prominent nucleoli, and abundant pale eosinophillic cytoplasm.


Frequent mitoses	Mart-1 (+)


S100 protein (+)	Calretinin (-)

Molecular Diagnostics

BRAF V600 image

BRAF mutation analysis was performed using the TrimGen Mutector™ II BRAF kit (TrimGen Corporation Sparks MD).
The incidence of the BRAF V600E mutation in metastatic melanoma is approximately 45% and the presence of this mutation is highly predictive of improved rates of overall and progression-free survival in patients with previously untreated melanoma who received the BRAF kinase inhibitor vemurafenib (PLX4032).

Chapman, et al. (2011). Improved survival inMelanoma with BRAF V600E mutation. NEJM; 364:2507-2516

Flaherty K et al.(2010). Inhibition of mutated, activated BRAF in Metastatic Melanoma NEJM; 363:809-819

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