Inflammatory Pseudotumor



Inflammatory Pseudotumor


Francisco Vega, MD, PhD





Key Facts


Terminology



  • Inflammatory reaction with multifactorial pathogenesis



    • Infectious etiologies account for subset of cases


Clinical Issues



  • Young adults with fever and constitutional symptoms


  • Localized or involving several lymph node groups


  • Excellent prognosis


Microscopic Pathology



  • Initially centered on hilum, trabeculae, and capsule of lymph nodes


  • Fascicles and whorls of spindle cells


  • Vascular proliferation


  • Polymorphic inflammatory infiltrate



    • Plasma cells often numerous


  • Pronounced follicular hyperplasia occurs in syphilitic lymphadenitis


Ancillary Tests



  • Spindle cells positive for markers of fibroblastic reticulum cells &/or histiocytes


  • Lack of chromosomal translocations involving ALK or lack of ALK1 protein expression


  • No evidence of monoclonality


Top Differential Diagnoses



  • Inflammatory myofibroblastic tumor


  • Kaposi sarcoma


  • Mycobacterial spindle cell pseudotumor


  • Follicular dendritic cell sarcoma


  • Hemorrhagic spindle cell tumor with amianthoid fibers (palisaded myofibroblastoma)







IPT focally involving mediastinal lymph node is characterized by spindle cell proliferation, slight sclerosis, and a polymorphic inflammatory infiltrate image. Note residual lymphoid follicle image.






IPT of lymph node is composed of spindle cells, histiocytes, and clusters of plasma cells and small lymphocytes.


TERMINOLOGY


Abbreviations



  • Inflammatory pseudotumor (IPT)


Synonyms



  • Plasma cell granuloma


Definitions



  • Inflammatory reaction involving lymph node characterized by proliferation of spindled cells associated with small vessels and inflammation


ETIOLOGY/PATHOGENESIS


Infectious Agents



  • Etiology is most likely multifactorial but subset appears related to infectious agents



    • Treponema pallidum


    • Pseudomonas veronii


    • Pseudomomas psittaci


  • Subset of IPT cases are associated with rheumatoid arthritis


  • For many cases etiology is unknown; EBV unlikely to be involved


CLINICAL ISSUES


Presentation



  • No sex predilection


  • Broad age range; median: 4th decade


  • Fever &/or constitutional symptoms


  • Anemia, elevated erythrocyte sedimentation rate, hypergammaglobulinemia


  • Localized or involving several lymph node groups



    • Cervical, axillary, mediastinal, retroperitoneal, and inguinal lymph nodes


Treatment



  • Surgical excision of lesion is curative


Prognosis



  • Excellent; usually self limiting



    • Relapse in some cases


MACROSCOPIC FEATURES


General Features



  • Enlarged; rubbery, gray-white cut surface


MICROSCOPIC PATHOLOGY


Histologic Features



  • Cell proliferation initially centered on fibrous network of lymph node



    • Hilum, trabeculae, and capsule


  • Different histologic stages



    • Stage I: Partial involvement; prominent inflammation


    • Stage II: More diffuse involvement


    • Stage III: Dense sclerosis; few inflammatory cells


  • Fascicles and whorls of spindle cells


  • Vascular proliferation (small vessels)


  • Polymorphic inflammatory infiltrate



    • Plasma cells common and can be numerous


    • Immunoblasts, small lymphocytes, histiocytes, neutrophils, and occasional eosinophils


    • Histiocytes can be spindled or round


  • Vasculitis is frequent


  • Follicular hyperplasia can be prominent



    • Suspect spirochete infection as cause


  • Lack of necrosis, karyorrhexis, or infarction


  • No cytologic atypia or atypical mitotic figures



ANCILLARY TESTS


Immunohistochemistry

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Inflammatory Pseudotumor

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