Cell kinetic analysis of interleukin-2 receptor-tested chronic lymphocytic leukemia using the AgNOR silver stain

B-cell chronic lymphocytic leukemia (B-CLL) is typically a low-grade neoplasm with a diploid DNA index and low proliferative activity. Interleukin-2 receptor (IL-2R/CD25) positivity often indicates increased proliferative activity and activation in both T and B lymphocytes. The argyrophilic nucleolar organizer regions (AgNORs) are loops of DNA identified by a silver staining technique and have been correlated with ploidy and proliferative activity. Two distinct AgNOR counting methods have been previously shown to correlate with DNA ploidy and proliferative activity, respectively: the mean AgNOR count (mAgNOR) correlates more with ploidy, and the percentage of nuclei with > or = 5 AgNORs/nucleus (pAgNOR) reflects proliferative activity. We studied bone marrow specimens from 32 patients with B-CLL using both anti-IL-2R on the marrow aspirates and the AgNOR silver stain on marrow biopsy specimens, applying both AgNOR counts. All tumors were CD5+, CD19+, and CD19/CD20+. Sixteen tumors were IL-2R- (< 20% IL-2+ B cells), and 16 were IL-2R+ (> or = 20% IL-2R+ B-cells). No significant difference in morphology of bone marrow involvement was noted in the two groups. A male predominance was noted in the IL-2R+ group of patients (3:1). There was also a preponderance of lambda light chain expression in the IL-2R+ tumors (11/16) compared with the IL-2R- cases (5/16). Except for two cases, all tumors had mAgNOR counts within the diploid range (< 2.4). The 16 IL-2R- tumors had pAgNOR in the range of 0% to 7% (mean, 2.31 +/- 2.18 standard deviation), whereas the IL-2R+ tumors had pAgNOR ranging from 6% to 15% (mean, 10.20 +/- 2.70 standard deviation; P < .0001). This finding suggests that IL-2R+ B-CLL might represent a subgroup of tumors with higher proliferative activity.