[1401] CD5-Negative Mantle Cell Lymphoma, a Potential Diagnostic Pitfall. A Single Institution's Experience in past 5 Years.

Xiaojun Wu, Hayward S Edmund, Vishnu VB Reddy. University of Alabama at Birmingham; Cunningham Pathology, St Vincent's Birmingham, AL

Background: In daily practice, the differential diagnoses for small cell sized lymphoma include Mantle cell lymphoma (MCL), CLL/SLL, MALT lymphoma, etc. Among these, MCL is a higher grade lymphoma and has a much worse prognosis. MCL is typically CD5+, CD23- and BCL1+. Therefore, CD5 is the common marker used to differentiate MCL from other CD5- lymphoma. However, the presence of CD5-MCL complicates the diagnostic algorithm. More importantly, misdiagnosis contributes to inappropriate therapeutic approaches and may have impact on patient's survival. This study aims to investigate the frequency of CD5- MCL, the frequency of undiagnosed CD5- MCL and the outcome of these CD5- MCL cases in our institution.
Design: The electronic documents of all lymphoma cases diagnosed from 1/1/2005 to 4/1/2010 in our institute were reviewed. All MCL cases with negative CD5 expression by immunostaining and/or flow cytometry were selected. Histomorphology of lymphoma, patient's presenting stage, their response to chemotherapy and their outcomes were assessed. Pearson chi square test was performed with p < 0.05 considered significant.
Results: A total of 93 MCL cases were identified in past 5 years in our institution. Of these cases, 19 were CD5- (20.4%). All cases had confirmatory BCL-1 immunohistochemistry or t (11; 14) FISH analysis. The patient's mean age was 70 year old (51 -88). The male/female ratio was 1.4. Seven of these CD5- MCL cases were previously classified as other lymphoma (37%), such as CLL and MALT lymphoma, which comprised 7.5% of all MCL cases.
Lymphoma cell size in MCL has been implicated in prognostication. In CD5- MCL, large cell size was found to be associated with poor response to chemotherapy (p = 0.019) but not significantly with poor outcome (p = 0.087). Ten of seventeen CD5- MCLs had intermediate to large cell size. All 15 staged cases presented as III to IV disease stage. In 12 cases with follow up, two cases stayed in complete remission, one patient died of MCL, and the remaining cases showed residual/recurrent disease.
Conclusions: We showed that a significant percentage of CD5- MCL cases (20%) was identified in our institution. Of these, 37% were previously diagnosed as low-grade B-cell lymphoma. However, most of CD5- MCL demonstrated an unfavorable outcome. Therefore, awareness of CD5- MCL cases in daily practice will improve diagnostic accuracy and patient care.
Category: Hematopathology

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 175, Monday Morning

 

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