[476] Evidence-Based Pathology: Low Cost-Effectiveness of CD3/CD20 Immunostains in Triage of Lymphoid-Rich Pleural Effusions

AE Walts, AM Marchevsky. Cedars-Sinai Medical Center, Los Angeles, CA

Background: CD3/CD20 immunostains are often performed in the cytologic evaluation of lymphoid-rich pleural effusions (LR-PE). Most benign LR-PE are predominantly composed of T(CD3+) cells while most malignant LR-PE are of B(CD20+) cell lineage. As part of the effort to contain laboratory costs, there is increasing interest in applying principles of evidence-based pathology to the use of immunostains.
Design: 258 consecutive LR-PE in which CD3/CD20 immunostains had been performed on cell blocks were retrieved from our cytology files. LR-PE had been diagnosed as reactive lymphocytosis or lymphoma/leukemia (L/L) based on morphology and immunophenotype. The utility of CD3/CD20 in diagnosis of L/L was assessed and the percentage of cases in which L/L was initially diagnosed in the LR-PE was determined by correlating the cytological findings with clinical information and laboratory data including flow cytometry, peripheral blood counts, lymph node and/or bone marrow biopsy results that were available at sign-out.
Results: Of the 258 LR-PE (from patients 22-95 years of age), 196 (76%) were reactive lymphocytosis and 62 (24%) were L/L (37 B-cell, 10 CLL/SLL, 6 T-cell, 4 PEL, 4 multiple myeloma, 1 AML). There was a previous diagnosis of L/L, concurrent diagnostic tissue, clinical evidence of persistent, progressive, or recurrent disease, and/or marked peripheral lymphocytosis in 44 (71%) of the L/L cases. A first diagnosis of L/L was made in the remaining 18 (29%) cases, comprising 7% of the LR-PE and 0.3% of all pleural effusions evaluated in our cytology laboratory during the study period. In 16 of these cases (12 B-cell lymphoma, 3 PEL, 1 multiple myeloma), the neoplastic cells were large with high grade features that mandated full lymphoma workup. Marked peripheral lymphocytosis was indicative of L/L in 8 of the 10 CLL/SLL cases. In 2 cases, comprising 0.8% of LR-PE, concurrent CBC was not available and CD20 positivity led to further workup and diagnosis of CLL/SLL in the LR-PE.
Conclusions: Our findings suggest there are very few scenarios where CD3/CD20 immunostains are cost-effective in the selection of LR-PE that warrant workup for an initial diagnosis of L/L as the prevalence of CLL/SLL first diagnosed in LR-PE is <1% and large cell L/L can be suspected on morphology and/or clinical parameters. Atypical hematopoietic cells should be further evaluated irrespective of CD3/CD20 stains. The results underscore the feasibility of applying evidence-based principles toward cost-effective use of immunostains in cytology.
Category: Cytopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 63, Wednesday Afternoon


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