Osteosarcoma in identical twins: A case report.

Osteosarcoma (OS) is the most frequent primary malignant bone tumor, if we exclude myeloma, a hematologic systemic disease. OS is relatively uncommon, with an estimated incidence of 600 cases per year in the United States. Among siblings is an even rarer phenomenon, with scattered reports throughout the English literature(1). We report the incidence of OS in identical twins. The first case is a low-grade OS arisen in the proximal tibia of a 25-year-old man, treated with en-bloc resection and reconstruction with allograft. The second one is a high-grade OS of the distal tibia of the 33-year-old twin, developed in a previous non-ossifying fibroma (NOF) followed over the time. The patient was treated with neo-adjuvant chemotherapy, en-bloc resection and reconstruction with allograft. Our literature review did not find any case of OS in identical twins, while 26 reports of OS in siblings are described.