Issues in the pathology of the myelodysplastic syndromes

The diagnosis and subclassification of myelodysplastic syndromes (MDS) are usually straightforward if the criteria established by the French-American-British Cooperative Group are carefully followed. Some cases can be diagnostically challenging, however. This article discusses some of the special diagnostic problems such as hypocellular MDS, MDS with fibrosis, and cases that show morphologic overlap with myeloproliferative disorders and acute leukemia. Additional problems sometimes encountered in the diagnosis of MDS such as extramedullary disease, associated lymphoproliferative disease, and the 5q-syndrome are also reviewed.