Review Question - QID 3264

Leiomyosarcoma is a spindle cell neoplasm with cigar-shaped nuclei.

Ewing's sarcoma primarily occurs in patients that are less than 20 years of age and is the 2nd most common (primary) malignant bone tumor in children. The etiology of Ewing's sarcoma is a 11:22 chromosomal translocation that produces the EWS/FLI1 fusion gene, which can be detected by polymerase chain reaction(PCR). Radiographic features of Ewings include a lytic, permeative lesion with layers of periosteal reaction creating an "onion skin" appearance. Gross pathology often appears similar to pus and histology includes sheets of round cells with large nuclei and small amounts of cytoplasm. Immunohistochemical staining is positive for CD99. Treatment consistently includes neoadjuvant multiagent chemotherapy followed by either surgical resection or radiation.

Neuroblastoma, primitive neuroectodermal tumors (PNET), Ewing's sarcoma, and embryonal rhabdomyosarcoma are all described in the AAOS Comprehensive Orthopaedic Review textbook as having round cell components. Other processes that are often described as having round cells include eosinophilic granuloma, lymphoma, myeloma, and round cell liposarcoma.