[1493] The Immunophenotype of Prolymphocytoid Transformation of Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma (CLL/SLL) Revisited

Shannon K Rathke, Jason C Chang, Alexandra M Harrington, Horatiu Olteanu, Steven H Kroft. Medical College of Wisconsin, Milwaukee, WI

Background: Although data on the immunophenotype (IP) of CLL/SLL in prolymphocytoid transformation (PLT) is sparse, references suggest that IP changes associated with increasing prolymphocytes (PLs) include brighter CD20 and surface immunoglobulin (sIg), gain of FMC7, and loss of CD5. The presence of increased PLs in CLL/SLL at presentation may cause differential diagnostic issues, particularly with the prolymphocytoid variant of mantle cell lymphoma. Thus, a detailed understanding of the IP of PLT of CLL/SLL is desirable.
Design: Database searches over 7 yrs yielded 17 cases of PLT of CLL/SLL with detailed flow cytometry (FC). PLT was defined as PLs ≥10% of lymphocytes in the blood of patients with either a well-established history of CLL/SLL or other diagnostic or strongly supportive pathologic features of CLL/SLL [e.g., proliferation centers in tissue, lack of t(11;14)]. 4- or 8-color FC included the following antibodies in all cases, except as specified: anti-CD5, CD10 (13), CD19, CD20, CD22 (12), CD23, CD38 (12), FMC7, and sIg. Antigen intensity was assessed relative to normal B cells, internally or in other samples from similar time frames. 20 morphologically conventional CLL/SLLs were used as controls. A typical CLL/SLL IP was defined as: CD5(+), CD10(-), CD23(+), FMC7(-), and underexpression of CD20, CD22, and sIg.
Results: An atypical IP was seen in 5/17 PLTs (29%): 3/5 had 2 atypical findings [2 cases FMC7(+) and bright CD20(+); 1 FMC7(+) and bright sIg] and 2 had 1 atypical feature [1 FMC7(+), 1 CD23(-)]. FMC7 was dim or partial in 3/4 of (+) cases. CD38 was (+) to varying degrees in 8/12 (67%). 3/20 conventional CLL/SLLs demonstrated an atypical IP: 1 bright sIg, 2 bright CD20, 1 CD23(-). 4/14 (29%) conventional CLL/SLLs were CD38(+). Only 1 PLT had FC available for review from pre-PLT, and the IP was typical at both times. The overall frequency of an atypical IP did not differ significantly between the 2 groups (p=0.428). Comparing individual antigens, only FMC7 differed significantly: 4/17 PLT vs. 0/20 typical CLL/SLL (p=0.036).
Conclusions: The majority of PLTs of CLL/SLL (12/17; 71%) display a characteristic CLL/SLL IP, and overall manifest a no greater frequency of atypical IP than conventional CLL/SLLs. However, FMC7 expression (usually dim or partial) was more frequent in PLT (24%) than in typical CLL/SLL (0%). Whether FMC7 expression is acquired at PLT, or whether FMC7(+) CLL/SLLs are at higher risk of PLT cannot be ascertained from this cohort.
Category: Hematopathology

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 263, Tuesday Afternoon


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