Review Question - QID 6443

Age is an important consideration in the differential diagnosis of small round blue cell tumors that include neuroblastoma, Ewing's sarcoma, small cell osteosarcoma, mesenchymal chondrosarcoma, Langerhans' cell histiocytosis, lymphoma, myeloma, and small cell lung carcinoma. Metastatic neuroblastoma is the most likely diagnosis in children younger than 5 years old. Ewing's sarcoma typically peaks at ages 5 years to 15 years of age. Lymphoma is most often seen in the 15-year to 40-year range, whereas myeloma is most common in persons older than 40 years of age. Metastatic lung carcinoma is also a disease of older individuals. Small cell osteosarcoma and mesenchymal chondrosarcoma are exceedingly rare diagnoses that more typically occur in the second and third decades. Of the choices given, Ewing's sarcoma is the most common and likely diagnosis in a 9-year-old child.