BCL6, MUM1, and CD10 expression in mantle cell lymphoma

Area of Science:

• Hematology
• Oncology
• Immunophenotyping

Background:

• Mantle cell lymphoma (MCL) typically expresses CD20, CD5, and cyclin-D1, with the characteristic t(11;14) translocation.
• Germinal center cell markers are usually absent in MCL, though aberrant phenotypes like CD5-negative or cyclin-D1-negative MCL have been reported.
• Limited cases of MCL with CD10 and/or BCL-6 expression exist.

Purpose of the Study:

• To determine the frequency of aberrant immunophenotypes, including CD10, BCL-6, and MUM1 expression, in a cohort of 127 MCL cases.
• To analyze the co-expression patterns of BCL-6, MUM1, and CD10 in MCL.
• To evaluate the diagnostic implications of aberrant phenotypes in MCL.

Main Methods:

• Immunohistochemical analysis of 127 MCL cases.
• Assessment of CD10, BCL-6, and MUM1 protein expression.
• Correlation of immunophenotypic findings with the characteristic MCL markers (CD20, CD5, cyclin-D1) and t(11;14) translocation.

Main Results:

• All cases were positive for CD20 and cyclin-D1; 96% expressed CD5 and 98% showed t(11;14).
• BCL-6 expression was found in 12% of cases, and MUM1 in 35%.
• CD10 positivity (≥30% neoplastic cells) was absent; only 3 cases showed 10-20% CD10 positivity. MUM1 was expressed in 67% of BCL-6 positive cases.

Conclusions:

• Aberrant immunophenotypes in MCL are infrequent but not rare.
• The presence of aberrant markers like CD10, BCL-6, or MUM1 does not exclude an MCL diagnosis in otherwise typical cases.
• Understanding these variations aids in accurate MCL diagnosis and subclassification.