Correlation Between Preoperative Magnetic Resonance Imaging and Surgical Margins with Modified Mohs for Dermatofibrosarcoma Protuberans

BACKGROUND Dermatofibrosarcoma protuberans (DFSP) is characterized by asymmetrical and poorly defined growth. Magnetic resonance imaging (MRI) has been proposed for the delimitation of this tumor. OBJECTIVES To study the utility of MRI in evaluating the depth of infiltration in DFSP and to compare the efficiency of clinical palpation with that of MRI in delimiting the invasiveness of DFSP. METHODS Observational, prospective study of DFSP cases. The MRI scans for all cases were compared with the exact histological infiltration plane obtained using modified Mohs micrographic surgery (MMS). RESULTS Forty-three DFSPs were included: 22 primary, nine recurrent, and 12 extirpated with positive margins. Sensitivity for detecting deep invasion was 58% on examination using palpation and 67% using MRI. CONCLUSIONS We present the largest series of DFSP cases studied using MRI published to date. In primary cases, MRI has greater sensitivity than palpation for detecting depth of infiltration (67% vs 58%). MRI seems to be useful in primary DFSP in locations other than the head, neck, and upper part of the thorax. MRI is not useful for confirming tumor persistence in extirpated DFSP with positive margins or for studying lateral extension in primary DFSP.