Which of the following conditions should be suspected as the most likely cause of these findings? A 69-year-old, previously healthy woman has been feeling increasingly tired and weak for 4 months. On physical examination, she is afebrile. There is no hepatosplenomegaly or lymphadenopathy. Laboratory studies show a hemoglobin of 9.3 g/dL, platelet count of 250,600/mm3, and WBC count of 6820/mm3. The appearance of the peripheral blood smear is shown in the figure.