Chondrosarcomas represent approximately 20% of primary malignant bone cancers, being known as the most frequent neoplasia of the anterior thoracic wall. In our case, we present a case of a primary sternal chondrosarcoma in a 50-year-old female patient that has been polychemiotherapy and radiotherapy treated for breast cancer. Despite the initial treated malignancy of breast cancer in the personal pathologic history of the patient, it was discovered that the sternal tumor was not a metastatic disease from the breast neoplasm. After multiple investigations, the patient was successfully treated for the sternal chondrosarcoma after a radical sternal resection with a chest wall reconstruction completed with two titanium plates that were anchored on the ribs and with the placement of methyl methacrylate mesh.