Clinicopathologic reassessment of primary cutaneous B-cell lymphomas with immunophenotypic and molecular genetic characterization.

Primary cutaneous B-cell lymphomas (PCBLs) may have particular clinicopathologic characteristics distinct from their lymph node-based counterparts. It has been suggested that PCBLs should have a separate classification system. The aim of this study was to determine whether the Revised European-American Lymphoid Neoplasms (REAL) classification is applicable to PCBL. Thirty-nine cases of PCBL from 36 patients, consisting of 20 men and 16 women (median age 66 yrs), were included in this study. Paraffin-section immunohistochemistry for CD3, CD5, CD10, CD20, CD43, Bcl-2, Bcl-6, and cyclin D1 was performed in all cases. Immunostaining for immunoglobulin light chains was also performed on cases histologically diagnosed as extranodal marginal zone lymphoma (MZL) and primary cutaneous B-cell lymphoma unclassifiable (PCBLu). Polymerase chain reaction (PCR) analysis of t(14;18) was performed in all cases. Immunoglobulin heavy chain gene rearrangement (VDJ) was tested by PCR on all follicle center lymphoma (FCL), MZL, and PCBLu cases. The 39 cases consisted of 15 (39%) FCLs, 13 (33%) diffuse large B-cell lymphomas (DLCL), 9 (23%) extranodal MZL, and 2 cases of PCBLu. Anatomically, 59% of PCBLs occurred in the head and neck, of which approximately 57% were FCL. Five of six cases presenting on the lower extremity were DLCL. Follow-up data was available from all 39 patients with a mean of 50.8 months. All but two patients are alive with or without disease at last contact. One patient with DLCL died of lung metastases and the other DLCL patient died of sepsis as a complication of therapy. In all 15 cases of FCL, CD10 and/or Bcl-6 expression supported the follicle center origin of the neoplastic cells. In contrast to previous reports, we found that 53% (8 of 15) of primary cutaneous FCL had either Bcl-2 protein expression or t(14;18). Our data indicate that many cases of primary cutaneous FCL have Bcl-2 alterations similar to their nodal counterpart. We found that 95% (37 of 39) of PCBLs could be classified according to the REAL classification, supporting its applicability in cutaneous lymphomas.