Plasma Cell Neoplasm (Plasma cell dyscrasia)

Plasma Cell Neoplasm (Plasma cell dyscrasia)

• Also known as Clonal plasma cell disorder.
• Characterized by the proliferation of monoclonal plasma cells.

Plasma Cells and Immunoglobulins

• Plasma cells produce immunoglobulins (antibodies).
• Normally, plasma cells are polyclonal.
• Plasma cell neoplasm involves the proliferation of monoclonal plasma cells.

Plasma Cell Neoplasms and Related Conditions

• Monoclonal gammopathy of undetermined significance (MGUS).
• Plasma cell myeloma and its variants.
• Other related disorders:
  • Plasmacytoma.
  • POEMS syndrome (osteosclerotic plasmacytoma).
  • Heavy chain diseases (HCD).
  • Primary amyloidosis.
  • Non-amyloid monoclonal light and heavy chain deposition diseases.

Detection of Clonal Plasma Cells

• Laboratory testing for M-component:
  • SPEP with reflex IFE (or CZS with reflex immunotyping, CZS/IT).
  • UPEP/IFE (not needed for diagnosis anymore).
  • Serum FreeLite assays & $\kappa: \lambda$ ratio (since 2001, for screening/diagnosis and monitoring).
• Bone marrow exam:
  • Morphology.
  • Flow cytometry and/or IHC.
• For associated bony lesions: X-ray, bone scan.
• Other lab testing: CBC, BUN/Cre, albumin, $\text{Ca}^{2+}$, $\beta_2$-microglobulin (MG).

Serum Protein Electrophoresis (SPEP)

• Prealbumin: PI 4.7, MW 54.4 Kd
• Albumin: PI 4-5.8, MW 66 Kd
• $\alpha$-region:
  • $\alpha$-antitrypsin: PI 4.8, MW 55 Kd
  • $\alpha$-acid glycoprotein: 2.7-4, 40 Kd
  • $\alpha$-lipoprotein/HDL (apo A): 200 Kd
  • $\alpha$-fetoprotein: 69 Kd
• $\alpha_2$-region:
  • Haptoglobin: 4.1, 5-1000 Kd
  • $\alpha_2$-macroglobulin: 5.4, 800 Kd
  • Ceruloplasmin: 4.4, 160 Kd
• $\beta$-region:
  • Transferrin: 5.7, 77 Kd
  • Hemopexin: 57 Kd
  • $\beta$-lipoprotein (apo B): ~3000 Kd
  • C4
  • Fibrinogen
  • C3
  • $\beta_2$-microglobulin
• $\gamma$-region: IgA, IgM, IgG, IgD, IgE, CRP

Serum and Urine M-component (Immunofixation electrophoresis, IFE)

• Discusses polyclonal vs. monoclonal Ig production.
• Illustrates SPEP and IFE results for serum and urine.

sFLC Assay (The Binding Site Inc)

• Serum FLC assay:
  • Developed in the early 2000s.
  • Uses polyclonal antibodies against the “hidden” epitopes of the light chain.
  • Performed by immuno-nephelometry.
  • Available on many automated chemistry analyzers and stand-alone instruments (e.g., SPAPLUS).
  • Two separate assays: one for kappa and the other for lambda.

sFLC assay results

• Normal reference intervals:
  • Free kappa: 3.3-19.4 mg/L
  • Free lambda: 5.7-26.3 mg/L
  • Kappa:lambda: 0.26-1.65

MGUS - Definition

• Serum monoclonal protein <3 g/dL (30 g/L) (30-40% MGUS has decreased normal Igs).
• No or only moderate Bence-Jones protein in the urine (< 1.0 g/24 hr) (one-third MGUS has BJP).
• <10% plasma cells in bone marrow.
• No end organ or tissue damage (absence of hypercalcemia, renal insufficiency, anemia, and bone lesions; CRAB).
• No evidence of B-cell lymphoma or other disorder known to produce an M-protein.

MGUS - Overview

• Prevalence: ~2% in age >50; ~5% in age >70.
• Can progress to myeloma/plasmacytoma (non-IgM MGUS), primary amyloidosis (non-IgM MGUS), IgM lymphoma (LPL)/WM (IgM MGUS), or CLL/SLL.
• The risk of progression to MM or related disorders is ~1% per year and indefinite (a pre-neoplastic condition).
• The concentration and type of monoclonal protein (IgM, IgA) are independent predictors of progression (~1.5% per year for IgM or IgA MGUS).
• Rarely, the paraprotein may disappear in 2-5% cases.

Plasma Cell Myeloma

• 1% of cancers; 10-15% of hematopoietic neoplasms.
• Incidence: ~5 per 100,000 per year (~20,000 new cases per year in the US).
• Age: 40-90 (median age at diagnosis is 70).
• M:F: ~1.4:1.
• White vs African American: 1:2.
• White vs Asian American: 2:1.

Plasma Cell Myeloma Details

• The most common lymphoid malignancy in blacks and the 2nd most common in whites.
• Represents 10-15% of all hematologic malignancies.
• Usually involves the vertebrae, ribs, skull, pelvis, femur, clavicle, and scapula.
• Serum monoclonal IgG – 50%; IgA – 20%; Light chain only – 20%; IgD – 2%; Bi-clonal – 1%; Non-secretory – 3%; IgM - <1%.
• Urine Bence-Jones protein found in ~75% of cases.
• Medium survival: 4-6 years.
• Remains to be incurable.

Multiple Myeloma – Clinical Features (‘CRAB’)

• Hypercalcemia (20%) – Skeletal destruction.
• Renal insufficiency (20-30%) – Tubular damage due to monoclonal light chain.
• Anemia (70%) – BM replacement; Renal damage with diminished EPO production.
• Bone pain/Fractures (70%) – Skeletal destruction.
• Recurrent infection – Depressed normal immunoglobulins (<50% of normal) (90%); neutropenia.
• Hyperuricemia (>50%); hypoalbuminemia (~15%; typically in advanced stage).

Myeloma – Lytic Bone Lesions

• Etiology: Genetic, environmental- viral.
• Leads to lytic bone lesions/fractures & hypercalcemia.

Myeloma – Rouleaux Formation

• Comparison of Red Blood Cell Agglutination and Rouleaux Formation.
• Rouleaux formation is caused by abnormal or increased plasma proteins (IgM Antibodies).
• Differentiated from specific agglutination.

Myeloma: WHO Classification

• Plasma cell myeloma (symptomatic).
• Clinical variants:
  • Asymptomatic (smoldering) plasma cell myeloma.
  • Non-secretory myeloma (~3% myeloma).
  • Plasma cell leukemia (2-5% of myeloma).

2008 WHO Criteria

• Calcium >10.5 mg/dL or UNL
• Creatinine >2 mg/dL
• Hgb
• Lytic bone lesions or osteoporosis with compression fracture

Diagnostic Categories

• MGUS: monoclonal gammopathy of undetermined significance
• SMM: smoldering multiple myeloma (asymptomatic)
• MM: Multiple myeloma (symptomatic)
• sFLC ratio $\geq$100 or BMPC $\geq$60%, No “CRAB”

International Myeloma Working Group (IMWG) Updated Criteria (2014)

• New criteria allow for myeloma diagnosis before organ damage, using validated biomarkers for SMM with ultra-high risk of progression.
• Free light chain (FLC) assays are incorporated for the first time.
• Cases without CRAB but with serum free light chain ratio of $\geq$100 and/or BMPC $\geq$60% are now classified as multiple myeloma, not smoldering myeloma.
• CT and PET-CT scans are recommended to identify bone lesions.
• CRAB: renal insufficiency CrCl

Plasma Cell Myeloma - Immunophenotype

• Monoclonal cytoplasmic immunoglobulin (Ig): ~85% have intact Ig, ~15% have light chain only.
• Flow cytometry: need permeabilization to determine clonality.
• CD45-/CD19-/CD20-/CD79a+/CD38+/CD43+, and CD117+ (~25% cases); CD10 and/or CD20 could be +.
• CD56 usually positive (CD56 - an adhesion molecule).
• CD138+ CD138 (Syndecan-1) is involved in the interaction with extracellular matrix.
• The most important IHC marker for myeloma.

Myeloma Staging (Durie & Salmon, modified)

• Stage I (low plasma cell burden):
  • Low M component: Serum: IgG <5 g/dL, IgA <3 g/dL; Urine: BJ <4 g/24h
  • Lytic bone lesions: Absent (except for solitary bone lytic lesion)
  • Hb: >10 g/dL; Serum calcium and Ig levels: normal
• Stage II (intermediate plasma cell burden):
  • Low M component: Serum: IgG 5-7 g/dL, IgA 3-5 g/dL; Urine: BJ 4-12 g/24h
  • Lytic bone lesions: present, multiple
  • Hb: normal or >8.5 g/dL; Serum calcium: normal or <12 mg/dL; Serum Igs: normal or mildly depressed
• Stage III (high plasma cell burden):
  • High M component: Serum IgG >7 g/dL or IgA >5 g/dL; Urine: BJ >12 g/24h
  • Lytic bone lesions: multiple, advanced
  • Hb:
  • A: Creatinine <2 mg/dL (IA, IIA, IIIA)
  • B: Creatinine >2 mg/dL (worse prognosis) (IB, IIB, IIIB)

Multiple Myeloma - New International Staging System (ISS) 2005

• Stage I:
  • Criteria: Serum $\beta_2$-microglobulin <3.5 mg/L & serum albumin $\geq$ 3.5 g/dL
  • Median Survival: 62 months (5 years)
• Stage II:
  • Criteria: Not stage I or III ($\beta<em>2$-microglobulin
  • Median Survival: 44 months (4 years)
• Stage III:
  • Criteria: Serum $\beta_2$-microglobulin $\geq$ 5.5 mg/L
  • Median Survival: 29 months (2.5 years)

Mott Cell (Russell Bodies)

• Russell bodies in BM aspirate smears.

Multiple Myeloma: Interactions Between Myeloma Cells and Bone Marrow Cells

• Myeloma cells interact with bone marrow stromal cells (BMSCs), bone marrow endothelial cells (BMECs), and osteoclasts.
• These interactions promote angiogenesis, myeloma cell growth, and bone reabsorption.

Multiple Myeloma: Pathogenesis

• Malignant proliferation of plasma cells leads to abnormal protein (immunoglobulin) production.
• This results in:
  • Skeletal destruction, leading to lytic bone lesions, pathologic fractures, and hypercalcemia
  • Marrow infiltration, resulting in pancytopenia and anemia, increasing risk of infection and bleeding
  • Abnormal proteins can cause kidney damage (Bence-Jones proteinuria), hyperviscosity (cryoglobulin), amyloidosis, and organomegaly.

Bone Destruction in Myeloma

• Myeloma cells and stromal cells secrete factors such as RANKL and MIP-1$\alpha$ that activate osteoclasts, leading to bone destruction.

The Wnt Signaling Pathway and Osteoblast Differentiation

• Wnt signaling promotes osteoblast differentiation.
• Factors like Sclerostin and DKK inhibit Wnt signaling.

The New Insight into the Formation of Osteolytic Lesions

• Myeloma cells secrete DKK1, which inhibits osteoblast activity, and RANKL, which activates osteoclasts, leading to bone destruction and osteolytic lesions.

Kidney Injury in Plasma Cell Myeloma

• Kidney injury can occur through:
  • Light chain cast nephropathy.
  • AL amyloidosis.
  • Monoclonal immunoglobulin deposition disease (MIDD).
  • Glomerulonephritis.

Nephrotoxicity of Monoclonal Free Light Chains

• Light chains are filtered by the glomerulus, absorbed in the proximal convoluted tubule, and can cause tubular and cast injury.
• High serum FLC levels correlate with increased urine FLC levels and kidney damage.

Multiple Myeloma - Prognosis

• Cytological features: Plasmacytic vs. plasmablastic vs. dysplastic/anaplastic.
• Degree of BM replacement: Stage I
• Proliferation index (Ki-67/MIB-1 $\geq$3%).
• Cytogenetics:
  • Unfavorable: deletion of 13q14, non-hyperdiploidy (hypodiploidy), +1q21, complex karyotype; deletion of 17p13, t(4;14) or t(14;16) or t(14;20) [FISH panel: 13q-, 17p-, 14q32 rearrangement].
  • Favorable: t(11;14), hyperdiploidy.
• Prognostic markers: Serum $\beta_2$-microglobulin, serum albumin, Hgb/Hct, serum calcium, level of M-component, serum creatinine.

Novel Therapies Targeting Myeloma Cells in the Bone Marrow Microenvironment

• Traditional therapies: MP (melphalan, prednisone), VAD (vincristine, adriamycin, dexamethasone).
• FDA Approved: Lenalidomide (Revlimid®), Bortezomib (Velcade®), Carfilzomib (Kyprolis®), Pomalidomide (Pomalyst®).

Other Plasma Cell Neoplasms

Monoclonal Immunoglobulin Deposition Diseases (MIDD)

• Primary amyloidosis (lambda type VI, V$\lambda$6).
• Light chain deposition disease (LCDD) (kappa type IV and I, V$\kappa$1 and V$\kappa$4).
• Other: Light and heavy chain deposition disease (LHCDD), Heavy chain deposition disease (HCDD).
• Affects Kidney, Lung, and BM.

Primary Amyloidosis

• Heart: CHF
• Liver: hepatomegaly
• Kidney: nephrotic syndrome and/or renal failure
• Intestine: malabsorption
• Tongue: macroglossia
• Nerves: neuropathy
• Vessel: bleeding (also due to binding of factor X)
• Initial Diagnosis Procedures:
  • Factor Xa assay
  • Rectal, abdominal fat and/or bone marrow biopsy