Plasma Cell Neoplasms (CH8, PFC and Gorczyca) Flashcards
What is the immunophenotype of
normal plasma cells ?
- bright for CD38 and CD138
- Note: CD138 is more sensitive and specific for plasma cells but it can be positive in non-hematopoietic malignancies as well
- CD19+, CD27+, CD43+, CD81+
- negative for CD20, CD22, CD56, CD117, CD200, HLA-DR and surface k/l
- CD27 is a memory associated antigen
- benign plasma cells can be dimly positive for CD45
What are the immunophenotypic changes
for abnormal/neoplastic plasma cells ?
- gain expression of additional markers by flow:
- CD28, CD33, CD56, and CD117
- usually show weaker CD38 and brighter CD138 as compared to normal plasma cells
*positive for CD43, MUM1, OCT2 and BOB1 - By IHC
- may be positive for EMA and Cyclin D1
- Occasional cases may be positive for CD20 and Pax-5
- rarely can be positive for CD19, CD20, CD27, CD33, HLA-DR and CD10 (IHC and flow), CD4 (may mimic AML)
- occasional cases may show loss of CD38 or CD138 expression
What is the importance of lack of CD56
expression by flow cytometry in neoplastic P.C. ?
- associated with fewer osteolytic lesions
- lambda light chain expressionn
- poorer prognosis
What is the expression of
CD28 in neoplastic plasma cells ?
- a gain of CD28 expression is seen about 50% of plasma cell neoplasms
- it correlates with poorer overall survival
What does the loss of CD27 expression
correlate with ?
- correlates with disease progression and worse overall prognosis
What aberrant expression of markers can be rarely seen
with plasma cell neoplasms ?
- positivity for:
- CD10
- CD33
- CD23
- HLA-DR
- lack of CD38
What is often seen with CD19+, CD20+
plasma cell myeloma ?
- rare to have both positive
- usually positive for CD27
- surface immunoglobulins are usually negative
- can be dim rarely
What does the expression of CD45 by
plasma cells correlate with ?
- proliferation rate
- in addition, proliferating myeloma cells are characterized by CD11a and BCL2 dim+
- CD45 expression
- recently shown to be an independent predictor of inferior overall survival among newly diagnosed plasma cell myelomas
How common in IgM MM ?
- very rare (< 0.5% of all myeloma patients)
- usually negative for:
- CD20
- CD56
- CD117
- may show aberrant expression of:
- CD19
- CD45
- Pax-5
NOTE: majority of these cases end up being positive for t(11;14) and Cyclin D1 by IHC
What is typically seen by flow cytometry
in patients with MGUS ?
- two populations of plasma cells
- polyclonal- normal
- monoclonal- neoplastic
What is the differential diagnosis
for PCM ?
- reactive plasmacytosis
- MGUS
- LPL/WM
- Mantle cell lymphoma
- B cell lymphomas with extensive plasmacytic differentiation
- Metastatic carcinoma (CD138 +)
- AML
- Pure erythroid leukemia (also CD45 -)
- B cell lymphomas with plasmacytic morphology
What conditions can lead to polytypic
plasmacytosis ?
- HIV infection
- chronic infection
- inflammatory disorders
- autoimmune disorders
- SLE, Sjogren’s syndrome
- drug eruptions
- Neoplasms
- AITL
- P. vera
- Aplastic anemia
- Hodgkin lymphoma
How can a plasma cell myeloma and a B cell
lymphoma with extensive plasmacytic differentiation
be differentiated by flow ?
- demonstrate that there is a clonal B cell population with monotypic expression of the same light chain immunoglobulin as the plasma cells.
- Lack of significant M protein
- Ex: Marginal zone lymphoma will not have a significant M protein and the clinical and radiographic findings will be different as well
What flow findings favor a PCM vs.
a B cell lymphoma with plasmacytic differentiation ?
- expression of two different light chains
- Lack of CD19 and CD45 expression
- presence of CD56 and or CD117 expression
- increased FSC
- plasma cells accompanying a small B cell lymphoma tend to be smaller with lower FSC
What can occasionally be seen
in Castleman Disease ?
- plasma cells may be monotypic IgA lambda
- must differentiate this from a PCM
