bcl-2 protein expression in primary cutaneous large B-cell lymphoma is site-related

Primary cutaneous large B-cell lymphoma (PCLBCL) that presents on the leg has recently been recognized as a distinct disease entity. These lymphomas have a reduced disease-free survival and a worse prognosis as compared with the more common, morphologically similar PCLBCL that present on the head or trunk. Studies in noncutaneous diffuse large B-cell lymphomas suggest a relationship between the expression of bcl-2 protein and clinical behavior. In the present study, we investigated whether these two groups of PCLBCL differ in the expression of bcl-2 protein and the presence of t(4;18), known as one of the causes of bcl-2 overexpression.

Paraffin sections from pretreatment biopsies of 14 PCLBCLs of the head or trunk and nine PCLBCLs of the legs were investigated for expression of bcl-2 protein using immunohistochemistry, and for the presence of the 14;18 translocation using polymerase chain reaction (PCR) amplification with primers against both the major breakpoint region (mbr) and the minor cluster region (mcr) of bcl-2. For reasons of comparison, nine secondary cutaneous large B-cell lymphomas (SCLBCLs) were also studied.

Expression of bcl-2 protein was found in all nine PCLBCLs of the leg and in all nine SCLBCLs, but not in any of the 14 PCLBCLs on the head and trunk. The t(14;18) was only detected in two of seven SCLBCLs, but not in the five PCLBCLs of the leg or the eight PCLBCLs on the head or trunk studied.

The striking differences in bcl-2 expression between PCLBCL of the head or trunk and PCLBCL on the leg suggest that bcl-2 expression is site-related and may contribute to the different clinical behavior between these two groups of lymphomas. In addition, they underscore that PCLBCL on the head and trunk and PCLBCL on the leg are distinct disease entities, as recently recognized in the European Organization for Research and Treatment of Cancer (EORTC) classification for primary cutaneous lymphomas.