A 56-year-old woman with a history of breast cancer that was treated 5 years ago with lumpectomy and radiation but with no
chemotherapy returns with bone pain, fatigue, and weakness. A complete blood count reveals severe anemia, as well as
decreased white blood cells and platelets. Examination of a peripheral blood smear reveals small numbers of nucleated red cells, as well as an occasional "blast" cell and myelocyte. A likely cause of the hematologic abnormalities is
ExplanationInfiltration of tumor cells from cancers, such as those of the breast and prostate, displaces bone marrow elements, thereby causing myelophthisic anemia. Chloramphenicol causes aplastic anemia in some individuals. Diphyllobothrium latum infestation can result in megaloblastic anemia due to vitamin B12 deficiency.