Interdigitating Reticulum Cell Sarcoma



Interdigitating Reticulum Cell Sarcoma


Wesley O. Greaves, MD

L. Jeffrey Medeiros, MD

Cyril Fisher, MD, DSc, FRCPath





Key Facts


Clinical Issues



  • Wide age range


  • Single lymph nodes most commonly involved



    • Cervical, axillary, or inguinal groups


    • Slow-growing, asymptomatic mass


  • Rare cases associated with B- or T-cell lymphomas or leukemias


Microscopic Pathology



  • Partial or complete replacement of lymph node architecture


  • Sheets, whorls, nests, or fascicles


  • Spindle-shaped or epithelioid cells


  • Cytologic atypia can be mild or prominent


Ancillary Tests



  • Immunohistochemistry



    • S100 strongly positive


    • Fascin(+)


    • CD68, CD45, lysozyme variable


  • Molecular genetics



    • HUMARA has shown clonality in small subset of cases tested


    • Antigen receptor genes are usually in germline configuration


    • No chromosomal translocations


    • IDC sarcoma in patients with follicular lymphoma carry IgH rearrangements and t(14;18)/IgH-BCL2


Top Differential Diagnoses



  • Langerhans cell sarcoma


  • Follicular dendritic cell sarcoma


  • Histiocytic sarcoma


  • Melanoma






Interdigitating dendritic cell sarcoma subtotally replacing lymph node shows that the neoplasm tends to spare lymphoid follicles. The neoplasm was S100 protein(+).






Interdigitating dendritic cell sarcoma involving lymph node shows that the neoplastic cells are spindled and epithelioid with abundant eosinophilic cytoplasm. A mitotic figure is present image.


TERMINOLOGY


Synonyms



  • Interdigitating dendritic cell (IDC) tumor


  • Interdigitating dendritic reticulum cell sarcoma


Definitions



  • Neoplastic proliferation of cells with immunophenotype similar to normal IDCs


ETIOLOGY/PATHOGENESIS


Postulated Normal Cell Counterpart is IDC



  • Antigen-presenting cell involved in T-cell immunity


  • Derived from CD34(+) lymphoid/myeloid progenitor cell in bone marrow that homes to lymph node


  • Normally found in



    • T-cell regions of lymph node


    • Periarteriolar lymphoid sheaths


    • Interfollicular areas of extranodal lymphoid tissue


Concept of “Transdifferentiation”



  • Rare patients with histiocytic neoplasms also have clonally related B-cell lymphoma



    • Usually B-cell lymphoma precedes histiocytic neoplasm



      • IDC sarcoma and follicular lymphoma


      • Histiocytic sarcoma and follicular lymphoma


      • IDC sarcoma and chronic lymphocytic leukemia/small lymphocytic lymphoma


      • Histiocytic sarcoma and splenic marginal zone lymphoma


    • Histiocytic neoplasms associated with follicular lymphoma share



      • t(14;18)(q32;q21)/BCL2-IgH &/or identical IgH gene rearrangements


    • Histiocytic tumors and nonfollicular B-cell lymphomas share identical IgH gene rearrangements


  • B-cell lymphoma might transform to histiocytic phenotype via “transdifferentiation”



    • Possibly due to loss of key components of B-cell differentiation


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Very rare


  • Age



    • Most patients are adults; median: 6th-7th decade


    • Youngest patient reported was 2 years old


  • Gender



    • Male to female ratio = 1.2:1


Site



  • Lymph node



    • Most commonly a single lymph node is involved


    • Cervical, axillary, or inguinal lymph node groups most often affected


  • Extranodal sites can be involved



    • Skin and soft tissue most common


    • Liver and spleen


    • Gastrointestinal tract, lung, kidney


    • Bone marrow is involved in < 20% of patients


Presentation

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Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Interdigitating Reticulum Cell Sarcoma

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