Telangiectatic osteosarcoma (TOS) is a rare malignant bone tumor. The main clinical and radiological significance of the case presentation is TOS can be easily misdiagnosed as a benign lesion such as an aneurysmal bone cyst (ABC). In this case, we present 63-year-old male with a large mass in the left leg. Imaging modalities were obtained in this patient to define the diagnosis. In this atypical case of TOS, relatively old age presentation, slow-progressing lesion, well-demarcated lesion, and lack of periosteal reaction further accentuate the similarity between TOS and ABC or other benign lesion causing high rate misdiagnosis of TOS. The histopathological examination will finally differentiate TOS from ABC.