Neutrophil CD64 is upregulated in RA patients with lymphoma but not in other solid cancers

Objective: To evaluate the utility of quantifying CD64 expression on neutrophils in rheumatoid arthritis patients with malignancy, especially its diagnostic role in lymphoma. Methods: We used flow cytometry to quantify CD64 expression on neutrophils from patients diagnosed with malignancy during the follow-up period prior to initiating treatment. Results: Neutrophils from 18 patients with lymphoma expressed significantly higher levels of CD64 (9635.6 +/- 2123.7 molecules/cell) than those from 32 patients with other solid cancers (carcinoma) (1250.5 +/- 91.1 molecules/cell) (p < 0.001). When the cutoff value was set at 2060 molecules/cell, the sensitivity and specificity of CD64 for diagnosing lymphoma was 88.9% and 94.4%, respectively. Conclusions: The quantitative measurement of neutrophil CD64 by flow cytometry may be useful as a subsidiary diagnostic marker in patients with suspected lymphoma. Although neutrophil CD64 is currently a well-known marker of infection, it is necessary to bear in mind that lymphoma is also a candidate in differential diagnosis when CD64 expression on neutrophils is upregulated.