A 13-year-old boy is brought to the physician because of progressive left leg pain for the past 2 months, which has started to interfere with his sleep. His mother has been giving him ibuprofen at night for "growing pains," but his symptoms have not improved. One week before the pain started, the patient was hit in the thigh by a baseball, which caused his leg to become red and swollen for several days. Vital signs are within normal limits. Examination shows marked tenderness along the left mid-femur. His gait is normal. Laboratory studies show a leukocyte count of 21,000/mm3 and an erythrocyte sedimentation rate of 68 mm/h. A representative sample is shown in the image. Which of the following is the most likely diagnosis?

Question

A 13-year-old boy is brought to the physician because of progressive left leg pain for the past 2 months, which has started to interfere with his sleep. His mother has been giving him ibuprofen at night for "growing pains," but his symptoms have not improved. One week before the pain started, the patient was hit in the thigh by a baseball, which caused his leg to become red and swollen for several days. Vital signs are within normal limits. Examination shows marked tenderness along the left mid-femur. His gait is normal. Laboratory studies show a leukocyte count of 21,000/mm3 and an erythrocyte sedimentation rate of 68 mm/h. A representative sample is shown in the image.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Eductional Objective: Ewing sarcoma is the second most common malignant bone tumor of childhood (after osteosarcoma).  It most commonly involves the lower extremity and pelvis and often metastasizes to the lungs.  Histopathology is characterized by uniform, small, round, cells; fibrous septae; and patches of necrosis and hemorrhage.

A 13-Year-Old Boy Is Brought to the Physician Because of Progressive