Background: Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are considered different tissue expressions of the same disease process, although they are clinically separable nosologic entities. A systematic comparison of the membrane phenotypes in the two entities needs to be investigated.
Methods: Cell suspensions from peripheral blood of 184 patients with CLL, bone marrow from 23 patients with CLL, and lymph nodes from 86 patients with SLL were analyzed to compare the membrane phenotypes.
Results: There were no significant differences between the three groups in the mean percentages of cells expressing surface immunoglobulin (SIg), CD5, CD19, CD20, and CD2 or in the frequency of cases with weak SIg. Although the mean percentage of mouse rosette-forming cells (MRFC) showed no statistical difference between bone marrow from CLL and lymph nodes from SLL, the mean percentage of MRFC in peripheral blood from CLL (48.02 +/- 18.23%) was twice as high as that in bone marrow from CLL (25.27 +/- 21.51%) and lymph nodes from SLL (20.87 +/- 16.72%) (P less than 0.001). Correlation analysis assessing the association of MRFC and residual T-cells showed a negative coefficient (r), and the r was statistically significant in bone marrow from CLL and lymph nodes from SLL but not in peripheral blood from CLL. The mean CD4/CD8 ratios in descending order were as follows: the ratio in lymph nodes from SLL (4.25) was greater than that in peripheral blood from CLL (1.70), which was greater than that in bone marrow from CLL (0.82); this followed the same pattern as the respective tissue controls. The mean ratios were not statistically different from those of their respective control groups.
Conclusions: The similarity of membrane phenotypes between CLL and SLL provided evidence that the two are different tissue expressions of the same disease. The alterations in CD4/CD8 ratios were related to the type of tissue analyzed and not to the disease process. The difference in MRFC presumably results from the microenvironment or residual T-cells.