Droplet digital polymerase chain reaction for the assessment of disease burden in hairy cell leukemia.

BRAFV600E mutation is the pathogenic driver of hairy cell leukemia (HCL) found in the vast majority of cases both at onset and during recurrences. The identification of the mutated allele in blood and marrow correlates with the presence of neoplastic cells and can be considered a marker of active disease. Likewise, the absence of the mutation after treatment may indicate a state of deep response. The BRAFV600E burden was measured by droplet digital polymerase chain reaction (ddPCR) and expressed as fractional abundance in 35 HCL patients at different stages of disease (onset, relapse, complete response [CR] after treatment, long-term remission) in peripheral blood and/or bone marrow (when available). Mean values of fractional abundance for patients at diagnosis, relapse and response, respectively, were 12.26%, 16.52% and 0.02% in peripheral blood and 23.51%, 13.96% and 0.26% in bone marrow. Four patients out of 6 evaluated at response were molecularly negative for BRAFV600E in peripheral blood. Mean fractional abundance in peripheral blood tested in 14 patients with long lasting CR was 0.05%, and 10 patients were BRAFV600E negative. These preliminary results suggest that ddPCR permits to assess the active tumor burden in HCL at different disease phases and support the hypothesis that some patients in CR qualify for a molecular CR.

Comparison of methodologies for the detection of BRAF mutations in bone marrow trephine specimens.

AIMS: BRAF V600E detection assists in the diagnosis of hairy cell leukaemia (HCL); however, testing practices vary. We evaluated the clinical utility of 5 BRAF mutation testing strategies for use on bone marrow trephines (BMT). METHODS: 11 HCL, 5 HCL 'mimic', 2 treated HCL and 10 normal BMT specimens were tested for mutant BRAF, comparing Sanger sequencing, pyrosequencing, amplicon-based next generation sequencing (NGS), automated (Idylla) PCR and immunohistochemistry (IHC). RESULTS: PCR and IHC were cheaper and identified V600E in 100 % of HCL cases. Pyrosequencing detected the mutation in 91%, NGS in 55% of cases and Sanger sequencing in 27%. All assays gave wild-type BRAF results in HCL mimics and normal BMT samples. CONCLUSIONS: PCR and IHC were most sensitive and cost-effective, but these have limited scope for multiplexing and are likely to be replaced by NGS gene panels or whole genome sequencing in the medium to long term.

Optimal primer selection for clonality assessment by polymerase chain reaction analysis: I. Low grade B-cell lymphoproliferative disorders of nonfollicular center cell type.

Recent polymerase chain reaction (PCR)-based studies focused on the detection of immunoglobulin heavy chain gene (IgH) rearrangements have suggested that clonal populations may be amplified more easily from certain categories of B-cell neoplasia than others and that primer makeup can be a critical factor in successful amplification. However, these particular reports contained relatively few low grade B-cell lymphoproliferative disorders of nonfollicular center cell type (LG-BLPD) and used only a limited panel of available primer sets for PCR amplification of monoclonal B-cell populations. To address this issue more extensively we evaluated 156 samples of LG-BLPD by the PCR to determine optimal primer selection in this setting. All cases were classified according to standard morphological and immunophenotypic criteria, with monoclonality documented by Ig light chain restriction analysis. The LG-BLPD included 33 cases of chronic lymphocytic leukemia (CLL), 57 cases of small lymphocytic lymphoma (SLL), 10 cases of atypical CLL, 32 cases of mantle cell lymphoma (MCL), 17 plasma cell neoplasms (PCNs), and seven cases of hairy cell leukemia (HCL). All primer sets included a 3' IgH joining region consensus primer, whereas the 5' IgH variable region (VH) primer was different in each set. The first-line panel included the following: Set 1, VH-framework III consensus primer, and Set 2, seven separate VH-framework I family-specific primers. A reserve panel of alternate VH consensus primers directed at framework II or III regions was used only when Set 1 showed no evidence of B-cell monoclonality.(ABSTRACT TRUNCATED AT 250 WORDS)