BRAF Mutation Analysis in Pulmonary Langerhans Cell Histiocytosis
Michal Kamionek, Mattew Welch, Keith Tomaszewicz, Lloyd Hutchinson, Ediz F Cosar, Karen Dresser, Armando E Fraire. UMass Memorial Medical Center, Worcester, MA
Background: Pulmonary Langerhans Cell Histiocytosis (PLCH) refers to an interstitial proliferation of Langerhans cells in the lung. PLCH is currently regarded as part of the spectrum of diseases associated with cigarette smoking. The nature of PLCH is not clear. Some regard it as a reactive process while others favor a true neoplastic process. Recently BRAF mutations have been identified in systemic and osseous variants of the disease. This study aims to analyze a series of PLCH patients for the BRAF mutation in the lung.
Design: Histopathologically documented cases (n= 10) of PLCH were evaluated for BRAF mutations. A total of 18 paraffin embedded tissue blocks from 10 cases were analyzed for BRAF mutation (some cases have multiple tissue blocks). Lesional areas were identified and microdissected. BRAF specific PCR reactions were performed with a peptic nucleic acid (PNA) clamp designed to block amplification of wild-type sequences between codons 598 and 602. Amplicons were analyzed by real time PCR. All results were confirmed by Sanger sequencing using capillary electrophoresis. The obtained sequencing data was then compared to a wild-type BRAF reference file to identify possible mutations.
Results: BRAF mutations were found in 5 cases out of 7 qualified cases (71.4%). One of 10 cases had no diagnostic tissue left in the block and two cases were rejected due to suboptimal DNA quality. Cases with multiple blocks showed (GTG>GAG) V600E mutation in all blocks tested. One of the cases showed an unexpected (ACA>ATA) T599I mutation in the BRAF gene.
Conclusions: Our findings suggest that BRAF mutations are common in PLCH, supporting the view that PLCH may be a neoplastic proliferative disorder. Our findings further suggest a potential benefit from FDA-approved drug vemurafenib targeting BRAF mutation. Deep sequencing for other possible mutations involving BRAF or other oncogenes may be useful in BRAF codon 600 wild type PLCH cases.
Tuesday, March 20, 2012 1:30 PM
Platform Session: Section D, Tuesday Afternoon