Importance of flow cytometric analysis of serous effusions in the diagnosis of hematopoietic neoplasms in patients with prior hematopoietic malignancies.

Objective: To determine the criteria for the use of immunophenotyping by flow cytometry (FCM) in the diagnosis of hematopoietic lesions.

Study design: A retrospective review of 89 consecutive body fluid specimens with concurrent FCM analysis during 2001 to 2006 was performed. The cytopathologic diagnosis was compared with the final diagnosis as modified by subsequent FCM.

Results: The cytopathologic diagnosis was benign in 61 cases (69%), atypical in 20 cases (22%) and malignant in 8 cases (9%). In patients without any prior clinical history, FCM study was positive in 2 cases and negative in 49 cases. In these patients, the working cytopathologic diagnosis was modified from benign/atypical to malignant in 2 (11%) cases and atypical to benign in 11 (33%) cases. In patients with a prior clinical history, FCM was positive in 23 cases and negative in 15 cases.

Conclusion: FCM studies were helpful in the cytopathologic diagnosis in 35% of body fluid specimens, permitting appropriate cancer staging and management. In the absence of a prior clinical history, immunophenotyping by FCM in body fluid specimens should be ordered after adequacy studies when there is cytologic atypia or a strong suspicion of malignancy on the cytopathologic diagnosis.