Feasibility of Counting Smudge Cells as Lymphocytes in Differential Leukocyte Counts Performed on Blood Smears of Patients With Established or Suspected Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma.

BACKGROUND: Lymphocytosis and smudge cells are commonly observed on the blood smears of patients with an established or suspected diagnosis of chronic lymphocytic leukemia/small lymphocytic lymphoma. Excluding smudge cells from the manual differential count (MDIFF), a common laboratory practice, yields unreliable results and consequently necessitates performing the MDIFF testing on an albuminized blood smear. OBJECTIVE: To assess the reliability of counting smudge cells as lymphocytes in the MDIFFs on nonalbuminized smears and automated differentials (ADIFFs) as a substitute for MDIFFs. METHODS: We compared corresponding results of MDIFFs on nonalbuminized smears vs MDIFFs on albuminized smears (group A, n = 82), ADIFFs vs MDIFFs on nonalbuminized smears (group B, n = 68), and ADIFF vs MDIFFs on albuminized smears (group C, n = 50). Smudge cells on the nonalbuminized smears were counted as lymphocytes. We focused on 2 white blood cell types: neutrophils and lymphocytes. RESULTS: Respective means for % lymphocytes and % neutrophils were 83.2 vs 83.2 and 14.0 vs 13.6 for Group A, 75.0 vs 77.0 and 20.2 vs 19.8 for Group B, and 76.1 vs 79.3 and 18.7 vs 17.4 for Group C. Respective correlation coefficients for % lymphocytes and % neutrophils were 0.92 and 0.94 for group A, 0.94 and 0.97 for group B, and 0.88 and 0.92 for group C. CONCLUSION: Counting smudge cells as lymphocytes on nonalbuminized blood smears yielded reliable MDIFF results. Reportable ADIFF results were generated by the analyzer on 73% of the specimens, of which 93% were reliable.

The utility of BRAF V600E mutation-specific antibody VE1 for the diagnosis of hairy cell leukemia.

OBJECTIVES: BRAF V600E mutation is characteristic of hairy cell leukemia (HCL). A V600E mutation-specific antibody, VE1, has been recently developed. We studied the diagnostic utility of this antibody in HCL and compared it with other B-cell neoplasms. METHODS: VE1 activity was assessed using immunohistochemistry in 90 mature B-cell neoplasms, including HCL (n = 17), HCL variant (n = 6), chronic lymphocytic leukemia (CLL) (n = 20), and 47 other B-cell lymphomas. Most (87/90) specimens were formalin-fixed, paraffin-embedded bone marrow (BM) biopsy specimens decalcified in either hydrochloric acid or formic acid. RESULTS: VE1 was positive in 15 (88%) cases of HCL and two (10%) cases of CLL and was negative in all other tumors assessed. The VE1-positive HCL cases showed uniform staining in all tumor cells, but intensity was variable. The two VE1-negative HCL cases had BRAF V600 mutations proven by molecular analysis. The two CLL cases positive with VE1 showed an atypical staining pattern with expression in a minority of lymphoma cells. Immunohistochemistry using the VE1 antibody had a sensitivity of 88% and a specificity of 97% for HCL. CONCLUSIONS: VE1 immunohistochemistry is a useful and convenient surrogate for detecting BRAF V600E mutation in BM biopsy specimens decalcified with hydrochloric or formic acid-based solutions.