[1592] CD34 Staining in Megakaryocytes Is Not Specific for Myeloid Malignancies and Has Minimal Diagnostic Value

Dava S West, Curtis A Hanson, Ellen D McPhail, James D Hoyer. Mayo Clinic, Rochester, MN

Background: CD34 is typically used as a surrogate blast marker in acute leukemias. Some studies have indicated that CD34 staining in megakaryocytes (MK) might be a diagnostic indicator of a myelodysplastic syndrome (MDS), while others have suggested that CD34 staining in MK is non-specific. The goal of this study was to reassess the use of CD34 in a variety of malignant and reactive hematologic conditions to determine its diagnostic value.
Design: 273 bone marrow (BM) biopsies were immunostained with CD34 (HPCA-1; BD Biosciences): MDS (n=54); myeloproliferative neoplasms (MPN; n=50); MDS/MPN (n=27); acute myeloid leukemia (AML; n= 35); normal BM (n=23); and BM with benign or non-myeloid malignant diagnoses (n=84). The latter included lymphoproliferative disorders (n=41), metastatic disease (n=17), reactive thrombocytosis (n=13), and immune thrombocytopenia (n=13). The % MK staining with CD34 was estimated (none, 1-10%, 10-30%, 30-60%, or 60-100%). The intensity (strong vs. weak) of MK CD34 staining was also determined.
Results: The Table shows the distribution of cases with negative or positive CD34 staining in MK; 86 cases were negative and 187 showed CD34+ MK. CD34+ MK were seen in all disorders and were not limited to MDS; 67% of non-myeloid/normal and 76% of MDS, MPN, & MDS/MPN cases had CD34+ MK. The number of MK that were CD34+ varied across all disease types with <10% CD34+ MK being the most common staining pattern. Only 27 of the 187 CD34+ cases had >30% CD34+ MK: 20 myeloid malignancies, 3 reactive MK hyperplasias, 2 ITP, and 2 normals. These 20 myeloid malignancies accounted for only 12% of the malignant myeloid cases. The intensity of MK staining with CD34 did not correlate with any disease category and was not helpful in the overall interpretation.

Conclusions: The data show that CD34 immunohistochemical staining in MK is likely a non-specific finding. CD34+ MK can be found in a wide variety of conditions, including immune thrombocytopenias or reactive thrombocytoses that may be confused with MDS or MPN. While staining in MK can be seen in cases of MDS and MDS/MPN, non-myeloid malignancies and normal BM can also have CD34+ MK. Thus, the finding of CD34+ MK cannot be used as an indicator of any malignant myeloid disorder, including MDS.
Category: Hematopathology

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 232, Tuesday Morning


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