plasma cell neoplasm


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  • Clinical Types

    • MGUS
      • M protein < 30 g/L, usually IgG
      • clonal plasma cells < 10% in marrow
      • asymptomatic
    • Myeloma
      • multifocal clonal plasma cells (vs plasmacytoma)
      • presence of M protein though 3% lack M protein (IHC shows cytoplasmic M protein)
      • Smoldering/asymptomatic
        • M protein > 30 g/L
        • and/or 10% clonal plasma cells in marrow
      • Symptomatic
        • M protein in serum or urine (usually > 30 g/L IgG, 25 g/L of IgA or 1 g/24hr of urine light chain)
        • clonal plasma cells in marrow, usually > 10%
        • CRAB: Ca, renal, anemia, bone lesions
      • Plasma cell leukemia: neoplastic cells 2E9/L or 20% of WBC in blood
      • unfavorable if
        • del 13, del 17p13
        • aneuploidy, hypoploidy
        • t(4;14), t(14;16) or t(14;20)
      • favorable if
        • lack unfavorable, and:
        • hyperdiploid
        • t(11;14), t(6;14)
    • Plasmacytoma
      • solitary plasmacytoma: single localized bone tumor
      • extraosseous plasmacytoma: single localized non-bone tumor
    • Immunoglobulin deposition disease
      • amyloidosis
      • light and/or heavy chain deposition disease
      • tissue deposit occurs before significant tumor burden
    • Osclerotic myeloma
      • clinical
        • associated with POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, skin changes)
        • most have low level serum M protein (lambda IgG or IgA)
      • morphology
        • focally thickened bone trabecula with paratrabecular fibrosis and entrapped plasma cells (may be stretched)
        • background normal plasma cells, usually < 5%
      • can have lymphadenopathy resembling plasma cell variant of Castleman disease

  • Morphology

    • blood: rouleaux
    • marrow: clusters of plasma cells
    • atypical plasma cells: nuclear immaturity (prominent nucleoli, higher NC ratio), pleomorphism
    • inclusions
      • Mott cells: multiple Russell bodies
      • Russell body: pink cytoplasmic
      • Dutcher bodies: nuclear, IgM
      • flame cells: flaming membrane, IgA

  • Stains

    • plasma cell markers: CD138, CD38
    • monoclonal kappa/lambda restricted (kappa > 4x or lambda > 2x)
    • aberrant loss of CD19 (nearly always)
    • aberrant gain of CD56 (~70%, except plasma cell leukemia), CD117, CD20
    • can be cyclinD1+ (ddx MCL), CD138 also stains squamous cells (ddx SCC)
    • normal plasma cells are polyclonal, CD138+, CD19+, CD56-

  • Molecular

    • 14q32 rearrangement (50%)
    • favorable: hyperdiploid, t(11;14), t(6;14)
    • unfavorable: hypodiploid, aneuploid, t(4;14), t(4;16), t(14;20), 17p13-, 13q-

  • Signout

    • Plasma cell neoplasm (***% plasma cells by manual aspirate differential count, ***% by CD138 analysis, and monotypic ***)
    • Molecular (Lymphoid mutation panel) studies are pending
    • Cytogenetic and FISH (plasma cell enrichment myeloma panel and CHIC-2) studies are pending
    • Microscopy: *** plasmacytosis with *** binucleated forms
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