Differentiation of chronic lymphocytic leukemia from other 'well to intermediate differentiated' lymphoproliferative disorders by the mouse rosette assay

The usefullness of the mouse rosette (MR) assay in differentiating among various 'well to intermediate differentiated' lymphoproliferative disorders (LPD) is presented. Thirty patients with a suspected LPD were studied. By standard histologic, cytologic, immunologic (surface immunoglobulin and monoclonal antibody markers), and clinical criteria, the following diagnoses (independent of MR data) were made: chronic lymphocytic leukemia (CLL)(n = 12), CLL in transformation (n = 2), well-differentiated lymphocytic lymphoma (WDLL)(n = 5), intermediate-differentiated lymphoma (IDL)(n = 2), hairy cell leukemia (HCL)(n = 3), prolymphocytic leukemic (PLL)(n = 1), poorly differentiated lymphocytic lymphoma (PDL)(n = 1), and no disease or reactive lymphocytosis (n = 4). There were 11 B-CLL cases and one T-CLL case. The percent of MR in all cases of B-CLL ranged from 26 to 76% (m = 62%); 10/11 cases had ≥ 50% MR. The case with 26% MR was atypical in that it occurred in a 26-year-old patient. The percent of MR ranged from 0 to 42% (m = 16%) in the cases of well to intermediate differentiated lymphomas. Similar to previous reports intermediate proportions of MR were seen in HCL (12-41%); and low values were seen in PDL (4%) and PLL (4%). In summary, the MR assay may be a useful tool for differentiating CLL from other well to intermediate differentiated LPD involving the peripheral blood. Also, since the MR receptor is normally found only on functionally immature cells, this differential mouse rosetting capability suggests that CLL arises from a less mature cell than WDLL or IDL.