Plasmacytoma/Multiple Myeloma
Background
What is the cell of origin in multiple myeloma (MM), and what does this cell usually secrete?
Mature B cells are the cell of origin in MM, and they usually secrete immunoglobulins that are also known as M proteins.
Approximately how many cases of MM are diagnosed annually in the U.S.?
~15,000 cases/yr of MM are diagnosed in the U.S.
What % of plasma cell tumors are MM? Solitary plasmacytoma (SP)?
MM constitutes 90% of plasma cell tumors, while SP constitutes 10% of plasma cell tumors.
Is there a racial or gender predilection for MM?
Yes, with regard to race. The incidence of MM is greater in blacks than whites (2:1). However, the incidence is similar among men and women.
What is the avg decade of life in which pts present with MM?
On avg, pts present with MM in the 5th–6th decades of life.
What environmental exposure is most strongly associated with MM?
Ionizing RT is strongly linked to MM, as seen in A-bomb survivors in Hiroshima.
What are the 2 forms of SP?
The 2 forms of SP are solitary bone plasmacytoma (SBP) and solitary extramedullary plasmacytoma (SEP).
What environmental or genetic alterations are consistently associated with MM?
There are no strong genetic or environmental patterns associated with MM. There may be a modest but increased risk of MM with exposure to RT (latency 20+ yrs) or the chemical alachlor, a commonly used pesticide.
What % of pts with SBP will progress to MM at 10 yrs?
SBP will progress to MM in 50%–80% of pts at 10 yrs. (Hu K et al., Oncology 2000)
What % of pts with SEP will progress to MM at 10 yrs?
SEP will progress to MM in 10%–40% of pts at 10 yrs. (Hu K et al., Oncology 2000)
What is the most common site of SEP?
The most common site of SEP is the H&N region (80% of SEP); the nasal cavity and paranasal sinuses are the most common subsites for SEP.
What is the relationship between secretory patterns in SBP vs. SEP?
Most pts with SBP have a secretory tumor, whereas most pts with SEP have a nonsecretory tumor.
What is the relationship between LN involvement in SBP vs. SEP?
SBP rarely involves LNs, but SEP will have LN involvement 30%–40% of the time.
What 3 lab abnormalities may prompt a clinician to evaluate for a plasma cell neoplasm?
Laboratory abnormalities that may prompt evaluation for a plasma cell neoplasm:
Unexplained normochromic/normocytic anemia
Unexplained renal insuffiency
Hypercalcemia
What lab tests are used for screening of a plasma cell abnormality?
Serum protein electrophoresis (SPEP) and urine protein electrophoresis (UPEP) are lab tests used to screen for a plasma cell abnormality. A positive screen on these tests results when a monoclonal population (or spike) is detected.
What is the common pattern of bone Dz in MM?
Lytic bone lesions are the most common bone abnormality seen on imaging of pts with MM.
What is monocloncal gammopathy of undetermined significance (MGUS), and how often will it transform to MM?
MGUS is a condition with clonal proliferation of an immunoglobulin in the absence of clinical, radiographic, or lab evidence of MM. The risk of transformation from MGUS to MM is 1%/yr.
What is 1 factor that predicts the risk of transformation from MGUS to MM?
The risk of transformation from MGUS to MM is predicted by the initial size of the M-protein peak.
What is the most common clinical Sx seen at Dx of MM or SP?
Bone pain is the most common clinical Sx seen at Dx of MM or SP. A subset of these pts will present with a pathologic fracture.
What is POEMS syndrome?
POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes) is a variant of MM with solitary or limited sclerotic bone lesions
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