title: Nodal marginal zone B-cell lymphoma with prominent follicular colonization - difficulties in diagnosis: a study of 15 cases.
abstract: OBJECTIVE
  While colonization of reactive follicles is well described in mucosa-associated lymphoid tissue lymphoma, this is not fully appreciated in nodal marginal zone B-cell lymphoma (NMZL). The aim was to address how to recognise this feature/entity and to discuss diagnostic difficulties faced by histopathologists in dealing with such lesions and their biological implications.
  
  
  RESULTS
  Fifteen NMZLs with prominent follicular colonization are described, 14 of which were referrals from other hospitals. All cases had a follicular pattern and showed prominent 'follicular colonization'. In many follicles the colonization was partial, and follicles also had a reactive germinal centre component. The phenomenon of follicular colonization was highlighted by immunohistochemistry. The benign follicle centre cells expressed CD20, CD10 and Bcl-6 and were negative for Bcl-2 and MUM1. In contrast, the colonizing marginal zone lymphoma cells expressed CD20, Bcl-2 and often MUM1 and were negative for Bcl-6 and CD10. Partially colonized follicles showed a 'moth-eaten' appearance on CD10, Bcl-2, Bcl-6 and MUM1 immunohistochemistry. In none except one was the referring diagnosis NMZL.
  
  
  CONCLUSIONS
  Recognizing and appreciating follicular colonization in a subset of NMZLs, appropriate use of immunohistochemistry and knowledge of immunohistological features can aid in making the correct diagnosis.
authors.affiliation: Department of Histopathology, Hammersmith Hospital & Imperial College, London, UK. k.naresh@imperial.ac.uk
authors.forename: K N
authors.initials: KN
authors.lastname: Naresh
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008198:Lymph Nodes / Q000737:chemistry / Q000473:pathology*; D018442:Lymphoma, B-Cell, Marginal Zone / Q000737:chemistry / Q000175:diagnosis*; D008224:Lymphoma, Follicular / Q000737:chemistry / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged
chemical_list: D014408:Biomarkers, Tumor