The presence of metaplastic ossification within atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDLPS) is a rare occurrence. When present, bone formation is most often found in association with a dedifferentiated component arising within the primary tumor. It is important for the radiologist not only to recognize the differential diagnosis of a calcified or ossified soft tissue mass but also be aware of the various soft tissue neoplasms, both aggressive and non-aggressive, that may show such features. We report a case of ALT/WDLPS with unusual extensive metaplastic bone formation without an element of dedifferentiated liposarcoma.