Osteosarcoma with rhabdomyosarcomatous component or so-called malignant mesenchymoma of bone.

BACKGROUND

Primary malignant mesenchymoma of the bone is a rare neoplasm consisting of two or more unrelated malignant mesenchymal components. The literature reports fewer than 20 cases, most of which were composed of osteosarcoma and liposarcoma.

OBSERVATION: We report an exceedingly rare case of primary malignant mesenchymoma of bone composed of rhabdomyosarcoma, osteosarcoma, and a minor chondrosarcoma component, arising in the right proximal humerus of a 15-year-old girl. The rhabdomyosarcomatous component was present in the initial biopsy and persisted in surgical specimen following chemotherapy.

CONCLUSION

Effect of chemotherapy is enigmatic since rhabdomyosarcomatous component could appear, persist or disappear after chemotherapy according to literature.