Osteosarcoma telangiectásico de fémur en un varón joven

telangiectatic osteosarcoma is a rare malignant lesion which constitutes about 2,5 % of all primary osteosarcomas. it has a more aggressive course than conventional osteosarcoma, as seen in large clinical series. by its clinical behavior, radiological and histopathological aspects, it is very similar to other benign tumors, such as aneurismatic bony cyst. we present here the case of a 24 year old male, with chronic pain in his left knee as only symptom. he was diagnosed with this rare form of osteosarcoma, amputated and then received a six month chemoteraphy regimen, after that, lung and thoracic wall metastasis were found. therefore, recognition of this variant of osteosarcoma and its differentiation from benign lesions is important because resection alone carries poor prognosis, whereas if chemotherapy is added to the treatment plan the life expectancy improves. this condition should be kept in mind in the differential diagnosis of limb pain among young and healthy people.