169. A 65-year-old woman comes to the physician because of a 10-week history of low-grade fever, fatigue, and pain in her right arm. She recalls no trauma to the arm. She has a history of cancer treated with radiation therapy. Her temperature is 37.7°C (99.8°F). Physical examination shows tenderness of the right distal humerus. Laboratory studies show anemia. An x-ray of the right upper extremity is shown. This patient most likely has an abnormality of which of the following cell types? A) Hematopoietic stem cells B) Monomyelocytic stem cells C) Natural killer cells D) Osteoclasts E) Plasma cells

169. A 65-year-old woman comes to the physician because of a 10-week history of low-grade fever, fatigue, and pain in her right arm. She recalls no trauma to the arm. She has a history of cancer treated with radiation therapy. Her temperature is 37.7°C (99.8°F). Physical examination shows tenderness of the right distal humerus. Laboratory studies show anemia. An x-ray of the right upper extremity is shown. This patient most likely has an abnormality of which of the following cell types? A) Hematopoietic stem cells B) Monomyelocytic stem cells C) Natural killer cells D) Osteoclasts E) Plasma cells