Periosteal chondrosarcoma is a low-grade, malignant cartilaginous bone neoplasm that arises on the surface of bone, predominantly in the metaphysis of long bones.

Periosteal chondrosarcoma is an infrequent chondrosarcoma subtype which accounts for less than 1% of all chondrosarcomas (1) and has a peak incidence in the fourth decade (2).

It has a reported incidence of local recurrences of 13-28% and a low metastatic potential, with distant recurrences occurring mostly in lungs (3).

Contrary to conventional chondrosarcomas, grading of periosteal chondrosarcomas seems not to predict prognosis. IDH1 and IDH2 mutations, characteristics of central chondromas/chondrosarcomas, have been also found in a subset of periosteal chondrosarcomas (1, 4).

These observations are based on the results from smaller series of cases (1, 5, 6), although the impact of histopathological characteristics on survival, local recurrence and metastases should be assessed in larger series of cases.

The aim of the present study is to review all the cases with a diagnosis of primary periosteal chondrosarcoma treated at the Rizzoli Institute from 1900 up to 31 December 2019, retrospectively.

The study will exam all the clinical, radiological, and histological features of this tumor with regard importance of medullary involvement, the IDH1/2 gene status, the types of treatment, the status of surgical margins, the presence of progression (dedifferentiation) areas and the relationship of these factors to individual outcome.

Inclusion Criteria:

• Male and female patients treated at Rizzoli Institute from 01 Jan 1900 to 31 Dec 2019
• Diagnosis of peristeal chondrosarcoma
• Written informed consent prior to any study-specific analysis and/or data collection

Exclusion Criteria:

• Patients with histological diagnosis different from periosteal chondrosarcoma.

Patients considered eligible will be included in the study, after providing a written informed consent.

Since we will include cases of several decades ago, and due to the high incidence of mortality of the disease under investigation, it would be possible that some eligible subjects will be deceased.