Dermatofibrosarcoma protuberans. A study of 148 patients.

Introduction. Dermatofibrosarcoma protuberans (DFSP) is the most common sarcoma of the skin. Although distant metastases are infrequent, DFSP is highly aggressive locally with frequent local recurrences. It has been reported that the presence within the tumour of areas histopathologically mimicking fibrosarcoma may increase the risk of recurrence. Objective. To review the clinical features of our patients with DFSP and the factors associated with recurrence of the tumour, focusing on the presence of fibrosarcomatous areas. Methods. Retrospective study of patients with DFSP diagnosed in 1990-2021 in a tertiary university hospital. The medical records were reviewed to obtain the following data: age, sex, tumour location, diameter, and evolution time, presence of fibrosarcomatous areas, development of recurrence, and follow-up. Factors possibly associated with disease-free survival were analyzed with Kaplan-Meier method and multivariate Cox regression. Results. 148 patients (74 women/74 men, mean age 46.28 years, SD 14.431) were included in the study. Tumours involved head and neck in 15 cases, thorax in 31, abdomen in 16, upper back in 43, lower back in 10, upper extremities in 10, and lower extremities in 23. Fibrosarcoma-like areas were observed in 16 tumours (10.81%) . In 17 patients (11.49%) recurrences were observed (13 local recurrences, 3 lung metastasis, and 1 local recurrence with lung metastasis). Fibrosarcomatous DFSP recurred more frequently than classic DFSP (50% vs. 6.82%, respectively), and its disease free survival was significantly lower (p<0.001). In multivariate Cox regression the presence of fibrosarcomatous areas was the only factor influencing disease free survival. Conclusions. It is important to identify the fibrosarcomatous variant since it recurs more frequently and has lower recurrence-free survival. Distant metastases, mainly in the lung, are also more frequent in fibrosarcomatous DFSP.