[1321] Analysis of Aberrant Expression of CD56 and CD117 in Plasma Cell Neoplasms.

Elizabeth A Morgan, Betty Li, Aliakbar Shahsafaei, David M Dorfman, Olga Pozdnyakova. Brigham & Women's Hospital, Boston, MA

Background: Plasma cell neoplasms are common hematopoietic malignancies that consist of a spectrum of disorders with a wide range of symptoms and outcomes. In the past decade, immunophenotyping by flow cytometry (FC) has become an important tool in the characterization of plasma cell disorders. Recent studies have identified several markers that are aberrantly expressed on malignant plasma cells, including CD56, a molecule involved in cell-cell and cell-matrix adhesion, which is expressed in up to 80% of plasma cell neoplasms. CD117, a tyrosine kinase transmembrane receptor expressed in bone marrow progenitor cells, may be aberrantly expressed in plasma cell neoplasms as well. The clinical and prognostic significance of aberrant marker expression remains unclear. While there is conflicting data regarding CD56 expression and prognosis, studies have shown that outcome is improved in patients with CD117-expressing myeloma cells. To our knowledge, no studies have compared concomitant expression of CD117 and CD56 in plasma cell myeloma cases.
Design: With the approval of the Institutional Review Board, we performed FC immunophenotyping for CD38, CD138, CD19, CD56, CD117 and cytoplasmic kappa and lambda on 85 biopsy-confirmed plasma cell myeloma cases, representing samples from 81 patients. Assessment for aberrant expression of CD117 was also performed by immunohistochemical (IHC) analyses. Cytogenetic analysis (karyotype and/or FISH) was performed in 59 cases (69%).
Results: Expression of CD56 and CD117 on malignant plasma cells by FC and results for cytogenetic studies are shown in TABLE 1. CD117 expression or lack of expression was confirmed by IHC in the 59 cases (69%) in which paraffin-embedded tissue was available.

TABLE 1. Pattern of expression of CD56 and CD117 on malignant cells by FC and correlation with karyotype

	CD56+CD117-	CD56-CD117+	CD56+CD117+	CD56-CD117-
No. of patients (%)	38 (45%)	11 (13%)	22 (26%)	14 (16%)
Karyotype and FISH
--Normal	13	8	15	8
--Hyperdiploid	8	0	4	2
--IGH rearrangement	3	1	2	3
--Other	3	1	2	3

Conclusions: A significant number of plasma cell neoplasms exhibited aberrant expression of CD56, CD117, or both markers. Addition of CD117 to the FC panel for suspected plasma cell neoplasms significantly increased the sensitivity of assay detection of neoplastic plasma cells from 71% to 86%. Expression of CD56 alone or concomitant with CD117 was associated with hyperdiploidy, which may represent a favorable prognostic subtype. Studies are underway to analyze the prognostic significance of CD56 and CD117 expression to help identify high-risk patients.
Category: Hematopathology

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 239, Tuesday Morning