Plasmablastic lymphomas with light chain restriction - plasmablastic extramedullary plasmacytomas?
BACKGROUND
It is diagnostically difficult to differentiate plasmablastic lymphomas (PBLs) from plasma cell neoplasms with plasmablastic differentiation. Plasmablastic lymphomas are currently classified as 'PBL of the oral mucosa' and 'PBL with plasmacytic differentiation'.


METHODS
Forty-five cases of PBL were retrieved from the Departments of Oral Pathology of the Universities of Pretoria and Limpopo, South Africa. Clinical features and HIV status were recorded and each case was classified as 'PBL of the oral mucosa type' or as 'PBL with plasmacytic differentiation'. Immunohistochemistry included: CD45, CD3, CD20, CD79a, CD38, CD138, MUM1, Ki-67 and kappa and lambda light chains. Positivity was recorded based on the percentage of positive staining cells as focal (5-20%); intermediate (20-70%) or diffuse (>70%). In situ hybridization was performed for Epstein-Barr virus (EBV) and HHV-8. Results were recorded as positive or negative.


RESULTS
All cases showed some degree of plasmacytic differentiation. All were negative for CD20 with reactive T cells detected with CD3. Diffuse and strong positive staining was found with Ki-67 and MUM1, but variable immunoreactivity was found with CD79a, CD45, CD38 and CD138. Twenty cases (47%) showed light chain restriction. Epstein-Barr virus was detected in 44/45 cases and HHV-8 in none.


CONCLUSIONS
The morphological classification of PBLs is not valid as all cases showed some degree of plasmacytic differentiation. We propose that PBLs with light chain restriction be reclassified as 'plasmablastic extramedullary plasmacytomas' and managed accordingly. The rest represents true PBLs. The true nature of these neoplasms as an entity should be further investigated with molecular and genetic studies.
Department of Oral Pathology and Oral Biology, School of Dentistry, Faculty of Health Sciences, University of Pretoria, South Africa. sonja.boy@up.ac.za
Sonja C
SC
Boy
Marlene B
MB
van Heerden
Erich J
EJ
Raubenheimer
Willie F P
WF
van Heerden
D000328:Adult; D002454:Cell Differentiation; D005260:Female; D006679:HIV Seropositivity / Q000150:complications; D004854:Herpesvirus 4, Human / Q000302:isolation & purification; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000032:analysis; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D016483:Lymphoma, AIDS-Related / Q000145:classification* / Q000276:immunology / Q000473:pathology / Q000821:virology; D016400:Lymphoma, Large-Cell, Immunoblastic / Q000145:classification* / Q000276:immunology / Q000473:pathology / Q000821:virology; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000473:pathology*; D009062:Mouth Neoplasms / Q000145:classification* / Q000276:immunology / Q000473:pathology / Q000821:virology; D010954:Plasmacytoma / Q000145:classification* / Q000276:immunology / Q000473:pathology / Q000821:virology; D012367:RNA, Viral / Q000032:analysis; D012189:Retrospective Studies; D013019:South Africa
C099537:Epstein-Barr virus encoded RNA 1; C106732:Epstein-Barr virus encoded RNA 2; D007147:Immunoglobulin Light Chains; D012367:RNA, Viral