Primary cutaneous B-cell lymphoma: a clinical, histological, phenotypic and genotypic study of 21 cases

The clinical, histological, phenotypic and genotypic features of 21 primary cutaneous B-cell lymphomas (CBCLs) have been investigated. The patients we re 13 men and eight women aged 34-91 years (median 67) at diagnosis. Eighte en patients had localized disease, and three had multiple skin lesions at d iagnosis, Twelve patients developed cutaneous or extracutaneous recurrences , and five died from malignant lymphoma 7-84 months (median 36) after diagn osis. Histological examination showed features of marginal zone/mucosa-asso ciated lymphoid tissue (MALT)-type lymphoma in 12 cases. Three of these had transformed to diffuse large B-cell lymphoma (DLBCL) in relapse biopsies. The remaining cases were seven primary DLBCLs and two cases tentatively cla ssified as follicle centre cell (FCC) lymphoma. The neoplastic B cells show ed similar phenotypes and genotypes in most cases (CD20+, CD79+, CD5-, CD10 -, cyclin D1-, bcl-2+ bcl-x-, bax-, t(14;18)-negative). p53 protein was exp ressed in five cases, and four harboured mis-sense or loss-of-function muta tions in the p53 gene. Deletion or promoter region hypermethylation of the p16(INK4a) gene was detected in two patients with DLBCL. The level of retin oblastoma protein expression and the proliferative fraction were significan tly higher in DLBCL (> 50%) than in MALT- or FCC-tppe lymphomas (<10%), Fea tures associated with an unfavourable prognosis were the presence of multip le skin lesions at diagnosis, transformation from MALT-type lymphoma to DLB CL, and possibly p16(INK4a) aberrations. It is concluded that most CBCLs ar e dissimilar from FCC lymphomas and seem to be more closely related to marg inal zone/MALT-type lymphomas. It is also suggested that there are fundamen tal differences between DLBCL and other histological categories of CBCL, in dicating that cutaneous DLBCL is a separate entity with an increased growth potential and genetic features similar to DLBCL originating in other anato mical sites.