Subcutaneous Panniculitis-like T-cell Lymphoma



Subcutaneous Panniculitis-like T-cell Lymphoma


Aaron Auerbach, MD, PhD





Key Facts


Terminology



  • T-cell lymphoma of αβ cells usually involving subcutaneous tissue with prominent karyorrhexis and cytotoxic phenotype


  • Cases composed of γδ cells are reclassified as cutaneous γδ T-cell lymphomas


Clinical Issues



  • 20% hemophagocytic syndrome


  • Excellent prognosis


Microscopic Pathology



  • Atypical lobular panniculitic T-cell infiltrate confined to subcutis


  • Malignant T cells rim around adipocytes


  • Prominent necrosis/apoptosis and angioinvasion


  • Vacuolated histiocytes


Ancillary Tests



  • Immunohistochemistry, TCR-βF1(+), TCR-δ(−), CD8(+), CD4(−), CD56(−), EBER(−)


  • (+) for cytotoxic markers


  • T-cell receptor gene rearrangement


Top Differential Diagnoses



  • Cutaneous γ/δ T-cell lymphoma



    • Panniculitis, but also in dermis &/or epidermis with ulceration, TCR-βF1(−), TCR-δ(+)


    • Worse prognosis than SPTCL


  • Lupus profundus panniculitis



    • Similar inflammation in subcutis in panniculitic pattern


    • Lobular panniculitis, but shows plasma cells and germinal centers unlike SPTCL







This clinical photograph shows a single nonulcerated subcutaneous nodule on the arm of a 35-year-old patient. Upon excision, the nodule was diagnosed as SPTCL. (Courtesy M. Tomaszewsky, MD.)






Low-power view of SPTCL shows malignant T cells confined to subcutaneous tissue image. The dermis image and epidermis image are both spared and are morphologically unremarkable. (Courtesy M. Tomaszewsky, MD.)


TERMINOLOGY


Abbreviations



  • Subcutaneous panniculitis-like T-cell lymphoma (SPTCL)


Definitions



  • T-cell lymphoma of αβ cells involving subcutaneous tissue with prominent karyorrhexis and cytotoxic phenotype



    • Cases composed of γδ cells are reclassified as cutaneous γδ T-cell lymphoma in the WHO Classification of Hematopoietic and Lymphoid Tumors


    • Subcutaneous T-cell lymphomas of γδ type are more aggressive than αβ cases


ETIOLOGY/PATHOGENESIS


Autoimmune Disease



  • Autoimmune disease present in ˜ 20% of patients



    • Systemic lupus erythematosus (SLE) most common



      • Microscopic findings of SPTCL overlap with lupus profundus panniculitis


Viral Infection



  • Rarely, SPTCL is seen with Epstein-Barr virus infection



    • May be due to immunosuppression


CLINICAL ISSUES


Epidemiology



  • Incidence



    • < 1% of all non-Hodgkin lymphoma



      • Presents sporadically without familial involvement


  • Age



    • Median: ˜ 35 years (range: 5 months to 84 years)



      • 20% < 20 years old


      • Rarely, children < 2 years old


  • Gender



    • Men = women


  • Ethnicity



    • No ethnic predisposition


Site



  • Extremities and trunk most common


  • Uncommonly disseminates



    • Can involve lymph nodes, but not at initial diagnosis


Presentation



  • Single or multiple erythematous subcutaneous nodules or plaques



    • Painless mass, rarely ulcerates


    • Symptoms due to mass effects


  • B symptoms in up to 50%



    • Diagnosis often not discovered until months to years after onset of symptoms


  • Hemophagocytic syndrome (HPS) in up to 20%



    • Related to release of cytotoxic molecules


    • May occur up to 5 years after presenting diagnosis


Laboratory Tests



  • Cytopenias (anemia, leukopenia, thrombocytopenia)


  • ↑ liver function tests


  • ↑ erythrocyte sedimentation rate, ↑ C-reactive protein


Treatment



  • Surgery



    • Sometimes excision of single lesion with no further recurrence


  • Immunosuppressive agents



    • Often given, at least initially


    • High-dose systemic corticosteroids


  • Chemotherapy



    • Recurrence or resistant cases treated with CHOP or CHOP-like therapy


  • Radiation



    • Sometimes for localized disease



  • Stem cell transplant



    • Can be considered for refractory/recurrent disease


Prognosis



  • Indolent disease



    • 5-year overall survival ˜ 80%


    • Mostly stage I (confined to skin)


    • Rare systemic spread



      • Including lymph nodes


      • Often years after diagnosis


  • HPS poor prognostic indicator



    • Medium survival ˜ 2 years


IMAGE FINDINGS


CT Findings



  • Enhancing nodules in subcutaneous tissue


MICROSCOPIC PATHOLOGY


Histologic Features



  • Atypical T-cell infiltrate of subcutaneous fat lobules



    • Involves lobules, usually spares septa



      • Uncommon septal pattern represents spilling of T cells from lobules


      • Typically, no tumor in overlying dermis or epidermis


    • Malignant T cells rim individual adipocytes



      • Characteristic, but not specific for SPTCL


    • Neoplastic cells



      • Small to large in size


      • Mild to marked atypia with irregular nuclear contours


      • Hyperchromatic nuclei


      • Pale, clear cytoplasm


  • Karyorrhexis (apoptosis) and fat necrosis characteristic



    • Necrosis from released cytotoxic molecules


  • Initial biopsy commonly shows minimal T-cell atypia



    • Later biopsies show more atypia


  • Angioinvasion in some cases



    • Poor prognostic indicator


  • Reactive inflammatory cells



    • Histiocytes



      • Vacuolated foamy cytoplasm from imbibed material/lipid


      • Erythrophagocytosis or cytophagocytosis


      • Sometimes poorly formed granulomas with multinucleated giant cells


    • Usually lacks plasma cells, eosinophils, or neutrophils


ANCILLARY TESTS


Immunohistochemistry



  • T-cell antigens (+) (CD2, CD3, CD5, CD7)



    • May lack 1 or more T-cell antigens


  • CD8(+)/CD4(−) in > 95% of SPTCL



    • CD4(−)/CD8(−) and CD4(+)/CD8(−) rarely


  • TCR-βF1(+), TCR-δ-1(−) (alpha-beta T cells)


  • Cytotoxic markers (+) (perforin, TIA1, and granzyme)



    • But GZM-M negative, unlike other T-cell lymphomas


  • CD56(−), CD30(−), Bcl-2(−)


Cytogenetics



  • No specific cytogenetic abnormalities


In Situ Hybridization

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Subcutaneous Panniculitis-like T-cell Lymphoma

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