8572 Background: Vemurafenib is currently the most active first-line treatment in MM patients that harbor BRAF-V600E mutations. The Cobas 4800 BRAF V600 Mutation Test is an FDA-approved, CE-marked test that identifies formalin-fixed-paraffin-embedded samples (FFPE) carrying the BRAF V600E mutation. Fine needle aspirates are frequently the only samples available in MM patients, but the use of CS has not been validated in this platform. We have evaluated the capability to identify BRAF-V600E mutations in CS of MM with the Cobas 4800 BRAF Mutation Test, and results have been compared to the conventional Sanger direct sequencing method. Methods: BRAF mutations have been studied in 117 samples from 98 MM patients with the conventional Sanger method: 37 (32%) FFPE and 80 (68%) CS. DNA was extracted from 4-micron sections in FFPE and from stained smears in CS. All CS contained >50% of tumor cells. In a second step, 57 out of the 117 samples have been studied using Cobas (25 CS and 32 FFPE). In CS, Nucleospin Tissue (Macherey-Nagel) DNA extraction was used in 17 cases and the Cobas procedure in 8. FFPE and CS paired samples were available in 9 patients. Results were compared using the Kappa coefficient. Results: There was 93% (53/57) agreement between Cobas and direct sequencing. All V600E+ cases were detected with both methods. Four V600R+ cases were negative using Cobas. Mean DNA concentrations using Nucleospin and Cobas procedures were 55.20 ng/µl and 11.37 ng/µl respectively. Concordance using Cobas in FFPE and CS paired samples was 100%. The table shows the results with Cobas and direct sequencing in 25 CS. One V600R+ case was not detected with Cobas. Conclusions: The Cobas 4800 BRAF Mutation Test results using CS containing >50% of tumor cells are identical to those obtained with FFPE. In our experience, DNA concentrations from CS with the Cobas method are lower than those obtained with Nucleospin procedure. These results provide a strong rationale for a larger validation study. [Table: see text]