[1339] Expression of CD10, BD6 and MUM1 in Mantle Cell Lymphoma

G Gualco, LM Weiss, WJ Harrington, CE Bacchi. Consultoria em Patologia, Botucatu, SP, Brazil; City of Hope National Medical Center, Duarte, CA; University of Miami Miller School of Medicine and Sylvester Cancer Center, Fogarty International Center (AIDS and Tuberculosis Program), Miami, FL

Background: Mantle cell lymphoma (MCL) characteristically expresses CD20, CD5 and cyclin-D1, carries the translocation t(11;14) (q13;q32) and typically has no expression of germinal center (GC) cell markers. So-called aberrant phenotypes such as CD5 negative and cyclin-D1-negative-MCL have been described. Also few cases with CD10 and/or bcl-6 protein expression have been reported.
Design: We analyzed 127 MCL organized in two tissue microarray (TMA), looking for the frequency of aberrant immunophenotype, including CD10, bcl-6 and MUM1 expression. MUM1, CD10 and bcl-6 were considered to be positive with 30% or more of the neoplastic cell nuclei stained for each marker. Interphase FISH analysis was performed on formalin–fixed, paraffin-embedded tissue included in TMA. For detection of the t(11;14))(q13;q32), a commercially available LSI IGH/CCND1 double-color-double-fusion probe was used (Abbott, USA). Whenever possible, at least 100 cells were analyzed.
Results: All cases were CD20 and cyclin-D1 positive, 96% expressed CD5 by immunohistochemistry. FISH on paraffin sections showed the t(11;14) in 98% of the cases. Bcl-6 expression was observed in 15 cases (12 %) and MUM1 in 45 cases (35%), in ten cases MUM1 immunostaining was strong with the remaining cases weak to moderate. Only 3 cases showed 10 to 20% of tumoral cells positive for CD10. No case showed CD10 positivity in 30% or more of the neoplastic cells. MUM1 expression was observed in 67% of the bcl-6 positive cases; 32% of the cases showed a MUM1+/bcl-6-/CD10- phenotype and 56% had a triple-negative-pattern.
Conclusions: Aberrant phenotype in MCL is infrequent but not rare, and when is present does not rule out a diagnosis of MCL in an otherwise typical case.
Category: Hematopathology

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 194, Wednesday Morning


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