Primary cutaneous large B-cell lymphoma shows activation of nuclear factor kappa B and low incidence of Epstein-Barr virus.

Primary cutaneous lymphomas are defined as lymphomas, which are present in the skin without evidence of extracutaneous disease at the time of diagnosis. Primary cutaneous large B-cell lymphoma (PCLBCL) is a subtype of primary cutaneous B-cell lymphoma with a female predominance, occurring in elderly patients and known to have unfavorable prognosis. We evaluated 10 cases of PCLBCL in immunocompetent patients between 2005 and 2008. A panel of immunoperoxidase stains; CD3, CD10, CD20, BCL2, BCL6, and MUM1 were performed on all cases. Nuclear factor kappa B (NF-kappaB) pathway activation was evaluated using an immunostain for P65. The presence of Epstein-Barr virus (EBV) was assessed using Epstein-Barr virus encoded RNA (EBER) in situ hybridization probe. All cases were CD20 positive and CD3 negative. CD10, BCL6, BCL2, and MUM1 were positive in 4/10 (40%), 6/10 (60%), 7/10 (70%), and 7/10 (70%) cases, respectively. NF-kappaB activation was detected in 7/10 (70%) cases. One (10%) case was positive for EBV by in situ hybridization. Interestingly, the EBV positive case was also positive for MUM1 and negative for CD10, indicating an activated immunophenotype. In conclusion, majority of PCLBCL shows activation of NF-kappaB pathway with a low incidence of EBV.