ASO-PCR assay and bone marrow histology. Top, ASO-PCR assay. PCR products were separated on 3% agarose gel electrophoresis, and for each sample, the wild-type (WT) and the mutant (M) allele were amplified. (A) HCL samples presented the BRAF V600E mutation, whereas the MW cases did not present the mutant allele. (B) Although B-CLPD cases 1 and 2 presented both the wild-type and the mutant allele, the SMZL case did not present the BRAF V600E mutation. An HCL sample with an heterozygous BRAF V600E mutation was used as a positive control, and a healthy donor was used as a negative control. Bottom, BM histology of case 1. (C) On BM biopsy, an abundant (60%) lymphoid infiltrate was observed with interstitial pattern and composed by small lymphocyte-like, centrocyte-like cells, without the typical morphology of hairy cells (Giemsa staining, ×40). (D) By immunophenotyping, either on histologic sections (here) or by flow cytometry on BM aspirate (Table 1), the only similarity between this case and HCL was the expression of cyclin D1/bcl1 oncoprotein (streptavidin-biotic-peroxidase complex method/SABC, DAB chromogen, ×40). (E) ANXA-1, the most specific marker of HCL, was negative on the lymphoid population, and only was expressed by myeloid precursors, which serve as internal control (SABC, DAB chromogen, ×60).