Reactive Paracortical Hyperplasia



Reactive Paracortical Hyperplasia


C. Cameron Yin, MD, PhD





Key Facts


Terminology



  • Predominantly T-cell response commonly seen in viral and drug-related lymphadenopathies


Clinical Issues



  • Patients typically present with enlarged lymph nodes, either localized or widespread


  • Systemic symptoms can be present


  • Size, location, and consistency of lymph nodes, as well as age and duration, are important factors in identifying etiology


Microscopic Pathology



  • Overall lymph node architecture is preserved


  • Paracortical areas are markedly expanded by heterogeneous population of cells



    • Small lymphocytes, histiocytes, and immunoblasts


  • Immunoblasts are large with prominent nucleoli



    • Can resemble Hodgkin or Reed-Sternberg cells


    • CD30(+), CD45(+), CD15(-)


Ancillary Tests



  • Normal T-cell immunophenotype


  • No evidence of monoclonal IgH or T-cell receptor gene rearrangements


Top Differential Diagnoses



  • Dermatopathic lymphadenopathy


  • Anaplastic large cell lymphoma


  • Myeloid sarcoma


  • Marginal zone B-cell lymphoma


  • Hodgkin lymphoma


  • T-cell/histiocyte-rich large B-cell lymphoma







Lymph node with reactive parafollicular hyperplasia demonstrates that the paracortical (interfollicular) area is markedly expanded. A residual follicle is at the top of the field.






A hyperplastic paracortex with a heterogeneous cell population is shown. Note the large immunoblasts with prominent nucleoli admixed with small lymphocytes and histiocytes.


TERMINOLOGY


Abbreviations



  • Reactive paracortical hyperplasia (RPH)


Synonyms



  • Diffuse paracortical lymphoid hyperplasia


  • Interfollicular hyperplasia, T-zone hyperplasia


Definitions



  • RPH is benign reaction, predominantly within paracortical regions of lymph node; manifestation of T-cell immunological response



    • Also occurs in extranodal lymphoid tissues


    • Often occurs as part of mixed reactive hyperplasia pattern


ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • Variety of environmental pollutants and chemicals can cause paracortical hyperplasia


  • Therapeutic agents (drugs) are an important cause



    • Phenytoin (Dilantin) and other antiseizure medications


  • Vaccine administration



    • Vaccinia


    • Measles (live, attenuated)


    • Usually arises 1-3 weeks after vaccination


Infectious Agents



  • Viral infection is common cause of RPH



    • Epstein-Barr virus (EBV)


    • Cytomegalovirus


    • Herpes simplex virus (type 1 or 2)


  • Necrosis is usually present in viral infection


CLINICAL ISSUES


Presentation



  • Patients present with enlarged lymph nodes, either localized or widespread


  • Systemic symptoms can be present



    • Fever, fatigue, and weight loss


  • Laboratory abnormalities may be present



    • Leukocytosis, lymphocytosis


  • Clues to etiology derived from



    • Patient age, duration of symptoms, and site


    • Size and consistency of lymph node(s)


Treatment



  • Localized lymph node enlargement in absence of other symptoms can be followed



    • If no resolution after 3-4 weeks, investigation is needed


  • Generalized lymphadenopathy is cause for concern



    • Immediate investigation for etiology is usually pursued


Prognosis



  • Self-limiting and reversible process with no impact on survival



    • Depends, in part, on underlying cause


  • Can be associated with other diseases (e.g., autoimmune diseases, malignancy)


IMAGE FINDINGS


Radiographic Findings



  • Lymphadenopathy, localized or generalized


MACROSCOPIC FEATURES


General Features



  • Lymph nodes mildly to moderately enlarged




    • No masses; lymph nodes usually not matted


  • Tan-white, soft cut surface


  • Focal necrosis may be discernible


MICROSCOPIC PATHOLOGY


Histologic Features



  • Overall lymph node architecture is distorted but preserved


  • Paracortical areas are markedly expanded by heterogeneous cell population



    • Immunoblasts in sea of small lymphocytes (mostly T cells) and histiocytes


    • Imparts a mottled or “moth-eaten” pattern at scanning magnification


  • Immunoblasts are large with vesicular nuclei and central nucleoli



    • Nucleoli are basophilic, often with trapezoidal shape


    • Nucleoli often have thin attachments to nuclear membrane (“spider legs”)


    • Can resemble Hodgkin or Reed-Sternberg (HRS) cells


    • Can form sheets in some cases (raising differential diagnosis of large cell lymphoma)


  • Eosinophils can be prominent



    • Particularly in hypersensitivity causes (e.g., drug reactions)


  • High endothelial venules often present


  • Other lymph node components can be reactive (so-called mixed pattern)



    • Reactive follicles


    • Monocytoid B-cell hyperplasia in sinuses


    • Nodules of plasmacytoid dendritic cells


Predominant Pattern/Injury Type



  • Lymphoid, interfollicular


Predominant Cell/Compartment Type



  • Lymphadenopathy


ANCILLARY TESTS


Immunohistochemistry



  • Small lymphocytes are usually immunophenotypically normal T cells



    • Positive for pan-T-cell antigens (CD3, CD5, CD7, CD43); CD4(+) and CD8(+) subsets


  • Immunoblasts can be of either T-cell or B-cell lineage



    • CD30(+), CD45(+), CD15(-)


  • Evidence of virus in EBV-associated cases



    • Positive for EBV-LMP


Flow Cytometry



  • Numerous T cells with normal immunophenotype


  • Fewer polytypic B cells

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Reactive Paracortical Hyperplasia

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