Diffuse Large B-cell Lymphoma, NOS, Immunoblastic



Diffuse Large B-cell Lymphoma, NOS, Immunoblastic


Francisco Vega, MD, PhD










DLBCL-IB shows large immunoblasts compared with the size of histiocyte nuclei image. Immunoblasts have a single, central, prominent nucleolus.






PET/CT scan of a patient with DLBCL-IB shows bulky lymphoma of the left neck image, right paratracheal space, retroperitoneum, spleen image, and vertebral bodies image.


TERMINOLOGY


Abbreviations



  • Diffuse large B-cell lymphoma, immunoblastic variant (DLBCL-IB)


Synonyms



  • Immunoblastic lymphoma


  • Immunoblastic sarcoma


Definitions



  • Diffuse proliferation of large neoplastic B cells with immunoblastic cytologic features



    • By definition, immunoblasts must be > 90% of all cells


  • Immunoblast



    • Large lymphocyte with centrally located nucleolus and moderate basophilic cytoplasm


  • DLBCL-IB variant superseded by specific types of DLBCL as defined in WHO classification


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Predominantly disease of older adults



      • Children and young adults can be affected


Presentation



  • Enlarging mass in nodal or extranodal sites


  • Gastrointestinal tract is frequent extranodal site


  • ˜ 1/3 of patients have stage IV disease


  • Bone marrow involvement less frequent than in patients with low-grade B-cell lymphomas


  • Frequent B symptoms (fever, night sweats, or weight loss)


Treatment



  • R-CHOP regimen (rituximab + cyclophosphamide, doxorubicin, vincristine, and prednisone)


Prognosis



  • Some studies have identified immunoblastic variant as being clinically more aggressive than centroblastic variant


  • 5-year overall survival for patients with DLBCL ranges from 25-75% depending on prognostic factors present at diagnosis


MICROSCOPIC PATHOLOGY


Histologic Features



  • Diffuse growth pattern



    • Irrespective of location, DLBCL-IB diffusely replaces normal architecture


  • Immunoblastic morphology


  • Plasmacytoid differentiation is common


ANCILLARY TESTS


Immunohistochemistry



  • Pan-B cell antigens(+)



    • CD20 can be dim, attributable to plasmacytoid differentiation


  • CD10(+), Bcl-6(+), LM02(+), HGAL(+) in subset


  • MUM1(+) in cases with plasmacytoid differentiation


  • FoxP1(+/-), Bcl-2(+/-), CD30(-/+), and usually weak and partial


  • Proliferation fraction (Ki-67) is usually high


  • Algorithms proposed to identify GC and non-GC types



    • Hans et al


    • Choi et al



DIFFERENTIAL DIAGNOSIS


DLBCL, Centroblastic Variant



  • Centroblastic and immunoblastic variants can be difficult to distinguish reliably



    • Justifies their inclusion into DLBCL as variants


  • By definition, at least a significant number (> 10%) of neoplastic cells are centroblasts


  • Subtle morphologic features supporting centroblastic variant



    • 2-3 nucleoli with 1 central and 1-2 apposed to nuclear membrane


    • Absence of plasmacytoid differentiation


    • Presence of small and large cleaved cells


    • Residual follicular pattern


DLBCL, Anaplastic Variant



  • Large neoplastic cells with bizarre morphology; may resemble Hodgkin &/or Reed-Sternberg cells


  • These neoplasms may have intrasinusoidal growth pattern


  • CD30 often positive

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Diffuse Large B-cell Lymphoma, NOS, Immunoblastic
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