Reactive Paracortical Hyperplasia

Reactive Paracortical Hyperplasia

C. Cameron Yin, MD, PhD

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.



  • Reactive paracortical hyperplasia (RPH)


  • Diffuse paracortical lymphoid hyperplasia

  • Interfollicular hyperplasia, T-zone hyperplasia


  • 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


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



  • 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)


  • 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


  • 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)


Radiographic Findings

  • Lymphadenopathy, localized or generalized


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


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



  • 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

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

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