IgM expression on paraffin sections distinguishes primary cutaneous large B-cell lymphoma, leg type from primary cutaneous follicle center lymphoma.
In the World Health Organization (WHO) 2008 classification 2 main types of primary cutaneous large B-cell lymphomas (PCLBCLs) are distinguished: primary cutaneous follicle center lymphoma (PCFCL) and primary cutaneous large B-cell lymphoma, leg type (PCBCL-LT). PCFCL has a 5-year overall survival rate of 95%, and PCBCL-LT of approximately 50%. Expression profiling studies have shown higher RNA expression of the IgM heavy chain in PCBCL-LT compared with PCFCL. To find out whether this difference could also be demonstrated at the protein level, we performed immunohistochemical staining for B-cell receptor heavy and light chains on skin biopsies from 53 patients with PCFCL and 40 patients with PCBCL-LT. All 40 cases of PCBCL-LT consistently showed cytoplasmic staining for IgM, in 18 of them with coexpression of IgD. In contrast, only 5 of the PCFCL cases showed cytoplasmic staining for IgM and/or IgD, including all 3 PCFCLs presenting on the leg. Hence, staining for IgM on paraffin-embedded sections seems to be an additional tool for differentiating between the 2 entities in clinical pathology practice. Analogous to other nodal and extranodal large B-cell lymphomas, expression of IgM in PCLBCL seems to be related to an activated B cell-like phenotype. Finally, the expression of IgM (and IgD) in this type of lymphoma might imply defective class switch recombination.
Koens
Lianne
L
Department of Pathology, Leiden University Medical Center, Leiden, The Netherlands. l.koens@lumc.nl
Vermeer
Maarten H
MH
Willemze
Rein
R
Jansen
Patty M
PM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007072:Immunoglobulin D / Q000378:metabolism; D007143:Immunoglobulin Heavy Chains / Q000032:analysis; D007147:Immunoglobulin Light Chains / Q000032:analysis; D007075:Immunoglobulin M / Q000378:metabolism*; D007866:Leg / Q000473:pathology; D008224:Lymphoma, Follicular / Q000175:diagnosis* / Q000276:immunology / Q000401:mortality; D016403:Lymphoma, Large B-Cell, Diffuse / Q000175:diagnosis* / Q000276:immunology / Q000401:mortality; D008297:Male; D008875:Middle Aged; D016612:Paraffin Embedding; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000276:immunology / Q000401:mortality; D015996:Survival Rate; D055815:Young Adult
D014408:Biomarkers, Tumor; D007072:Immunoglobulin D; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007075:Immunoglobulin M