Patho-anatomical features of so-called Ph1− chronic myeloid leukemia

Summary Chronic myeloid leukemia without the Philadelphia chromosome (Ph^1– CML) is described and distinguished from chronic myeloid leukemia with the Philadelphia chromosome (Ph¹⁺ CML) on the basis of clinical and autopsy findings of four cases. Ph^1– CML showed clinical, hematological, and patho-anatomical features which could be regarded as typical.Patho-anatomically Ph^1– CML differed from Ph¹⁺ CML in the variable maturation of the leukemic proliferation in the bone marrow and extramedullary infiltrates. Up to the terminal phase Ph^1– CML can be of an extremely mature cell type. However, it can also show myeloblastic transformation after an initially mature cell stage. Ph^1– CML infiltrates are found in tissues and organs which Ph¹⁺ CML usually does not infiltrate or only to a low degree until a blastie crisis.On the basis of its course and clinical and patho-anatomical features Ph^1– CML looks like an atypical chronic myeloid leukemia. However, it is better called an acute myeloid leukemia of the mature cell type.The authors are grateful to Mr. K.-H. Tedsen for his excellent technical assistance and to Mrs. M. Soehring for translation and secretarial help.