After obtaining Institutional Review Board approval, all patients diagnosed with DFSP and FS-DFSP between 1982-2009 were identified from the database of the Pathology Department of Musculoskeletal Oncology at the Rizzoli Institute. Two pathologists (M.G. and G.S.) reviewed the slides. Tumors were classified according to the Enzinger & Weiss criteria: FS-DFSP were identified by the presence of fibrosarcomatous changes (more than 5 mitoses/10 HPF, a "fascicular" growth pattern, increased cellularity and atypia) in at least more than 5% of tumor tissue . Immunohistochemical expression of CD34 (Qbend-10, 1-100 dilution, Dako, Carpinteria CA, USA) and Apo-D (36C6, 1-200 dilution, Novocastra, New-castle-on-Tyne, UK) were assessed by two pathologists (M-G. and L.Z.) in all patients with adequate tumor tissue. Detection of the two antibodies was performed on a Dako automated immunostainer with universal detection kit streptavidin biotin-alkaline phosphatase/red/detection system Dako after heat (Apo-D) and enzyme (CD34) induced antigen retrieval.
All patients surgically treated at our institution with histological diagnosis confirmed were included in the analysis. After 1986, the staging consisted of a computed tomography scan (CT-scan) and/or magnetic resonance imaging of the primary lesion, and a chest CT-scan; other specific tests (bone scan, abdomen CT-scan) were performed only in the case of clinical suspicion. Prior to 1986, a plain chest X-ray and ultrasound of the lesion were performed. Assessment of the surgical margins was based on both the pathology report and the description of the surgical excision. All patients were followed-up with ultrasound, computer tomography or magnetic resonance imaging studies at three to four-months intervals for at least two years, and subsequently at six-months intervals for another three years.
Pattern of recurrence for localized patients were defined as follow: local recurrence, when tumor relapse was confined to the primary tumor area; metastases, for distant only metastases: local recurrence plus metastases for local and distant recurrence.
The following parameters were examined for prognostic value in patients with localized disease: patient sex, tumor anatomic site, surgical margins, histology, CD34 and Apo-D expression, number of previous surgical treatment, use of radiotherapy.
The following categories were compared: tumor site (extremity: at or distal to the shoulder joint and in the groin or leg; trunk: proximal to the shoulder joint and the groin); surgical margins (adequate: wide or radical; inadequate: intralesional, marginal or contaminated margins, according to Enneking's classification); histology (DFSP vs. FS-DFSP); CD34 and Apo-D expression (positive or negative), number of previous operations (0 or ≥ 1); adjuvant treatments (radiotherapy performed within 3 months after tumor excision).
We analyzed overall survival (OS) and event-free survival (EFS). OS time was calculated from the time of admission at our Institute to death or last follow-up visit. EFS time was calculated from the time of admission at our Institute and the occurrence of an event. An event was defined as local recurrence, distant recurrence or death (disease-related or unrelated). All time-to-event end points were modeled using the method of Kaplan and Meier and analyzed by the log-rank test. The results of the Cox model analysis are reported as relative risks (RRs) and 95% confidence intervals (CIs).