Cytology and flow cytometry of malignant effusions of multiple myeloma

Identifying malignant plasma cells in body fluids from multiple myeloma pat ients is important for therapeutic and prognostic considerations. This can be difficult when plasma cells are mature in appearance or low in number. W e examined the cytological and flow cytometric findings of myelomatous pleu ral and pericardial effusions from 8 patients with advanced multiple myelom a. Cytoplasmic immunoglobulin light chain excess vs. DNA ploidy in the plas ma-cell population was evaluated by flow cytometry (FCM). The cytology smea rs of one pericardial and 14 pleural effusions from the 8 patients were rev iewed. Screening Papanicolaou-stained smears facilitated the detection of m alignant nuclear features; however, morphology of plasma cells was best see n in Diff-Quik-stained smears. Low cellularity and inadequate air-drying of smears accounted for the false-negative cytology seen in two-fluids from a single patient. A malignant plasma cell population was identified in 9 of 10 fluids submitted for FCM, including the two fluids with negative cytolog y. The false-negative FCM was from a suboptimal specimen wit high backgroun d staining. Six fluids had an aneuploid DIVA content, and four were diploid . A combination of Papanicolaou- and Diff-Quik-stained smears is recommende d for the evaluation of plasma cells in effusions from patients with multip le myeloma. Cytology and flow cytometry confirmed malignancy in 87% and 90% of fluids evaluated, respectively; all cases were diagnosed by either one or both methods. Our results suggest that FCM and cytology of serous effusi ons in multiple myeloma patients are complementary and should be used in di fficult cases. Diagn. Cytopathol. 2000;22:147-151. (C) 2000 Wiley-Liss, Inc .