Frequency of central nervous system involvement in primary cutaneous B-cell lymphoma

Primary cutaneous B-cell lymphoma (CBCL) constitutes approximately 20% of all primary cutaneous lymphomas. Apart from primary cutaneous large B-cell lymphoma presenting on the legs (PCLBCL-leg), primary CBCLs run an indolent clinical course, rarely disseminate to extracutaneous sites, and have an excellent prognosis. Because of recent observations in two patients who developed central nervous system (CNS) involvement, follow-up data of all primary CBCL patients registered at the Dutch Cutaneous Lymphoma Group between 1985 and 1998 were investigated for evidence of CNS involvement.

Follow-up data from 160 primary CBCLs were evaluated. This group included 122 primary cutaneous follicle center cell lymphomas (PCFCCLs), 16 primary cutaneous immunocytomas or marginal zone B-cell lymphomas, and 22 PCLBCL-leg.

Of all 160 patients with primary CBCLs, 11 died of lymphoma, including 4 of 122 patients (3%) with PCFCCL and 7 of 22 patients (32%) with PCLBCL-leg. Four of these 11 patients, including 3 with PCFCCL and 1 with PCLBCL-leg, had developed CNS involvement 3-93 months (median, 30 months) after diagnosis. All patients died 1-9 months (median, 7 months) after the development of CNS involvement. In the group of 122 patients with PCFCCL, CNS involvement occurred in 3 of 7 patients (43%) who developed extracutaneous disease and accounted for 3 of 4 lymphoma-related deaths (75%).

The results of this study indicate that approximately 2% of all primary CBCLs may develop CNS involvement. Whereas, in rare PCFCCL patients, developing extracutaneous disease CNS involvement was an important cause of death, patients with PCLBCL-leg and secondary CBCL died more frequently due to involvement of non-CNS organ systems.