Primary Cutaneous Follicle Center Lymphoma



Primary Cutaneous Follicle Center Lymphoma


Aaron Auerbach, MD, PhD





Key Facts


Terminology



  • PCFCL


  • Mature B-cell lymphoma of follicle center cells, primary to skin and not originating in another anatomic site


Clinical Issues



  • Mostly single lesion on scalp; trunk 2nd most common site


  • > 95% 5-year survival with local recurrences


Microscopic Pathology



  • Nodular, diffuse, and nodular/diffuse growth patterns


  • Lack of mantle zones, lack tingible body macrophages


Ancillary Tests



  • CD20(+), Bcl-6(+), CD10(+/−) (often negative in diffuse variant)


  • Bcl-2(−/+) and MUM1(−)


  • CD23, CD21, and CD35 positive in FDC meshworks


  • Usually CD43(−), unlike other B-cell lymphomas


  • CD5(−), Bcl-1(−)


  • Clonal Ig heavy chain (IgH) gene rearrangement


  • t(14;18), often not detected


  • Gene expression profiling findings akin to germinal center-like large B-cell lymphoma


Top Differential Diagnoses



  • Reactive follicular hyperplasia


  • Primary cutaneous marginal zone lymphoma


  • Secondary skin involvement of follicular lymphoma


  • Primary cutaneous diffuse large B-cell lymphoma, leg type


  • Primary cutaneous diffuse large B-cell lymphoma, NOS







There is a single large raised red nodule image on the scalp, 5 cm in largest dimension. Microscopically, the nodule was diagnosed as PCFCL. (Courtesy M. Tomaszewski, MD.)






Low-power magnification shows PCFCL with a multinodular image dermal infiltrate that is separated from the epidermis by a grenz zone image. (Courtesy M. Tomaszewski, MD.)


TERMINOLOGY


Abbreviations



  • Primary cutaneous follicle center lymphoma (PCFCL)


Synonyms



  • Follicular lymphoma of skin


  • Crosti disease (reticulohistiocytoma of dorsum)



    • Plaques/tumors surrounded by erythematous macules/papules


Definitions



  • Mature B-cell lymphoma of follicle center cells, primary in skin



    • Disease limited to skin for 6 months after diagnosis


  • Distinct disease from systemic follicular lymphoma



    • Better prognosis


    • Fewer BCL2 rearrangements than systemic follicular lymphoma


CLINICAL ISSUES


Epidemiology



  • Incidence



    • 0.1-0.2 cases per 100,000 people per year


    • Most common primary cutaneous B-cell lymphoma



      • ˜ 20% of all skin lymphomas


      • ˜ 60% of all B-cell skin lymphomas


  • Age



    • Usually adults



      • Median age: 60 years


      • But can also be seen in childhood


  • Gender



    • Male:female = 1.5:1


Site



  • Usually head and neck, especially scalp



    • Less commonly trunk


Presentation



  • Usually single lesion



    • ˜ 15% multifocal


  • Plaques, nodules, or tumors of differing sizes



    • From < 1 cm to > 40 cm in greatest dimension


  • Rarely ulcerates


Treatment



  • Observation, surgical removal or local radiation


  • Chemotherapy only if extensive disease or extracutaneous disease


Prognosis



  • Good



    • Much better than systemic follicular lymphoma


    • Usually complete remission with treatment


    • ˜ 95% 5-year survival


  • Not affected by



    • Grade or growth pattern


    • Bcl-2 expression or t(14;18) status


  • ˜ 35% recurrence (often proximal to original lesion); extracutaneous spread ˜ 10%


  • ˜ 10% disseminate to extracutaneous sites


MICROSCOPIC PATHOLOGY


Histologic Features



  • Dermal B-cell infiltrate, often extends into subcutis (˜ 75%)



    • No overlying epidermotropism


  • Growth pattern



    • Nodular, diffuse, or nodular and diffuse


    • May be classified as follicular (> 75% follicular architecture), follicular and diffuse (25-75% follicular architecture), or diffuse (< 25% follicular architecture) growth pattern


  • Follicles



    • Often not well-defined


    • Usually seen in small lesions



    • Lack mantle zones


    • Lack tingible body macrophages


    • Contain follicular dendritic cells


  • Tumor cells



    • Mostly centrocytes (small to medium-sized, cleaved)


    • Variable numbers of centroblasts (larger in size)


  • Cases with ↑ numbers of centroblasts



    • Diagnose as PCFCL if nodular or nodular and diffuse growth pattern


    • Diagnose as diffuse pattern PCFCL if large cells and only diffuse growth pattern


  • Grading of follicular lymphoma



    • Not necessary or of prognostic value for PCFCL


    • Is necessary for systemic follicular lymphoma



      • Grade 1: < 5 centroblasts per high-power field; grade 2: 6-15 centroblasts per high-power field; grade 3: > 15 centroblasts per high-power field


      • Grades 1 and 2 show minimal differences in long-term outcome


      • Thus, 2008 WHO classification lumps cases with few centroblasts as “follicular lymphoma grade 1-2 (low grade)” in systemic follicular lymphoma, and does not advise grading of PCFCL


Cytologic Features



  • Small cleaved cells with coarse chromatin and 1 or more indistinct nucleoli on peripheral smear


ANCILLARY TESTS


Immunohistochemistry

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Primary Cutaneous Follicle Center Lymphoma

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