IMMUNOHISTOCHEMICAL STUDY ON THE DIFFERENTIATION OF HYPOPLASTIC MYELODYSPLASTIC SYNDROME AND APLASTIC ANEMIA

Abstract

Both myelodysplastic syndrome （MDS） and aplastic anemia （AA） are types of bone marrow （BM） failure characterized by pancytopenia. Hypocellular-MDS （Hypo-MDS） is observed in approximately 15% of MDS cases, however, the number of hematopoietic cells is small, and morphological differentiation between MDS and AA is often difficult. The identification of tumor cells and non-tumor cells using immunohistochemistry in BM pathological tissues can aid in the differentiation of Hypo-MDS and AA. An appropriate and rapid pathological diagnosis of Hypo-MDS and AA is critical because of their varying treatments and prognosis; moreover, the time period prior to treatment is important. We investigated the usefulness of immunohistochemical （IHC） studies in the differentiation of Hypo-MDS and AA using BM pathological tissue diagnosis. BM clot sections or BM biopsy specimens were obtained from 40 Hypo-MDS/AA patients. Hypo-MDS had a BM cellularity of ‹30% in patients less than 70 years and ‹20% in those over 70 years. IHC and hematoxylin-eosin staining were performed. Indicators of p53, HbF, CD34, c-KIT, and megakaryocytic dysplasia may result in abnormal Hypo-MDS expression. In contrast, indicators of CD8-positive T-cells tended to accumulate in AA. The subtype analysis of mast cells showed no significant difference between the two diseases. The distribution of monocytes/histiocyte in BM tissue identified by CD68 and CD163 was not useful in the differentiation of Hypo-MDS and AA. We suggest that combining the indicators related to hematopoietic cells with those related to a BM background can improve differentiation of Hypo-MDS and AA in cases with a small number of hematopoietic cells, thus improving the accuracy of BM pathological diagnosis.