Primary desmoplastic small round cell tumor of the femur: Case report and review of a rare intraosseous malignancy


Advocate Children's Hospital


Desmoplastic small round cell tumors (DSRCT) are malignant neoplasms of young males arising most commonly in the abdominopelvic cavity, with a subset originating from extra-abdominal soft tissues. As either primary or metastatic lesions, they are rare in intraosseous sites. We describe the fifth report of primary DSRCT of bone. A healthy 18-year old male presented with a blastic, 17 cm lesion within the left distal femur, suspicious for osteosarcoma or Ewing sarcoma. Subsequent biopsy revealed nests of small round blue cells infiltrating through a desmoplastic stroma. These cells were diffusely positive for epithelial markers, with paranuclear staining for desmin and focal reactivity with NSE. Break-apart FISH revealed a rearrangement in , and RNA fusion panel confirmed as its partner in the pathognomonic t(11;22)(p13;q12) rearrangement. PET/CT showed widespread metastatic disease to visceral and bony sites. : Due to their rarity as well as clinicopathologic and immunomorphologic overlap, primary intraosseous DSRCT can create diagnostic challenges with the more frequently encountered tumors of bone.

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