follicular lymphoma


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  • Clinical

    • 20% of lymphoma
    • site: mostly nodes

  • Morphology

    • closely packed follicles effacing nodal architecture
    • neoplastic follicles lack polarization
    • monomorphic (mostly centrocytes, minor component of centroblasts)
    • can have marginal zone cells, plasmacytic differentiation, signet ring cells
    • marrow: tumor is paratrabecular
    • cytology
      • centrocyte: smaller, cleaved nuclei, inconspicuous nucleoli
      • centroblast: larger, vesicular chromatin, 1-3 peripheral nucleoli
      • follicular dendritic cells: dispersed chromatin, single nucleoli

  • Architecture Pattern

    • follicular: > 75% follicular
    • follicular and diffuse: 25-75% follicular (report approx %)
    • focally follicular: < 25% follicular (report approx %)
    • diffuse: 0% follicular (give disclaimer if small bx)
    • in situ FL: normal node, some follicle contains BCL2+ FL cells

  • Centroblast Grading

    • 1: 0-5 centroblasts per hpf
    • 2: 6-15 centroblasts per hpf
    • 3A: > 15 centroblasts per hpf
    • 3B: sheets of mostly centroblasts
    • report DLBCL component if any centroblasts area > 15 per hpf

  • Stains

    • follicular meshwork: CD21, CD23
    • neoplastic follicles positive: BCL2, BCL6, CD10
      • CD10 loss in grade 3B
    • Ki67 proliferation index correlates with grade

  • Molecular

    • t(14;18)
    • BCL2 (chr 18) rearrangement with IGH (chr 14)

  • Signout

    • Follicular lymphoma, grade ***
    • Microscopy: lymph node with architectural effacement by closely packed follicles lacking polarity and comprised of small to medium sized cells with *** centroblasts
    • Stains
      • CD3 stains the T cells
      • CD20, CD10, BCL2, BCL6 stains the neoplastic cells
    • FISH for t14;18 is pending
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