T2 STIR coronal
A 57-year-old male patient with a history of a neglected subcutaneous mass located in the left mid-thigh for almost two years, presents for recent changes in the aspect of the overlying skin, which consisted of ulceration and active bleeding.
The MRI sequences show a well-defined ovoid mass measuring 33/41/55 mm (tr/ap/cc) located subcutaneously at the postero-lateral aspect of the left mid-thigh, associated with mild edematous infiltration of the surrounding subcutaneous tissue. The lesion demonstrates an intermediate signal on T1WI (compared to the muscle) and high signal on T2WI/STIR, with moderate heterogeneous enhancement on post-contrast studies, which suggests intratumoral necrosis. On post-contrast studies there is also visualisation of the cleavage plane with the underlying biceps femoris muscle and ilio-tibial tract.
Dermatofibrosarcoma protuberans (DFSP) is a rare dermal tumour with an incidence rate of 0.8 to 4.5 cases per million persons per year, occurring most frequently in 30-40-year-old adults, without a gender-related predominance. It manifests a low metastatic rate but, a significant subclinical locally aggressive behaviour. [1,6]
Clinically, DFSP typically presents as an asymptomatic, slow-growing red-brown indurated plaque which eventually develops multiple nodules. Rarely it can ulcerate and bleed, as in the present case. DFSP is known to have implacable growth with profound projections which cannot be assessed on clinical exam, hence the importance of the imaging examination. [2,3]
On imaging studies, DFSP commonly appears as a well-defined nodular mass involving the skin and subcutaneous tissue. Ultrasound is essential for the primary evaluation of such superficial masses: characterizes its size, structure (solid vs cystic), vascularity, compressibility, extent. It is used as the initial imaging modality because of its availability, portability, and low cost. 
In our case, the lesion appeared as a heterogeneously hypoechoic solid mass, with significant posterior acoustic enhancement, which made it impossible to appreciate its deep limits. Therefore, MRI was the next step.
On CT, it shows soft-tissue attenuation values. On MRI it appears hyperintense on T2-WI and PD and hypointense on T1-WI, with suppression on fat-saturated sequences. Both on CT and MRI the lesion may exhibit heterogeneous contrast enhancement, as it undergoes necrotic or cystic degeneration. [2,4]
An important feature for the therapeutic attitude is the tumour's infiltration into the adjacent structures. In our case, MRI indicated a cleavage plane towards the muscular compartment, which is a favourable feature for a clean excision with little chance of recurrence, hence the justified decision for surgical removal of the mass, with post-op histopathological examination.
Imaging studies are not specific, since they may not distinguish DFSPs from other soft tissue sarcomas. Therefore, histological examination is the only definitive diagnostic method. 
The immunohistochemical examination is also decisive in the differential diagnosis of other tumours. 
The treatment is surgical, taking into consideration the high rate of local recurrence.
DFSP typically originates in the dermis and tends to infiltrate the underlying structures. In our case, the tumour was confined to the skin and subcutaneous tissue, but presented with ulceration and necrotic degeneration. When facing a superficial tumour with such clinical and imaging properties, it is important to take into consideration the diagnostic of DFSP, even in the presence of rare complications.
Written informed patient consent for publication has been obtained.
 Brooks J, Ramsey ML. Cancer, Dermatofibrosarcoma Protuberans. [Updated 2020 May 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513305/ (PMID: 30020677)
 Paramythiotis D, Stavrou G, Panagiotou D, Petrakis G, Michalopoulos A. Dermatofibrosarcoma protuberans: a case report and review of the literature. Hippokratia. 2016;20(1):80-83. (PMID: 27895450)
 Llombart B, Serra C, Requena C, et al. Guidelines for Diagnosis and Treatment of Cutaneous Sarcomas: Dermatofibrosarcoma Protuberans. Sarcomas cutáneos: directrices para el diagnóstico y tratamiento. Dermatofibrosarcoma protuberans. Actas Dermosifiliogr. 2018;109(10):868-877. (PMID: 30539729)
 Al Barwani AS, Taif S, Al Mazrouai RA, Al Muzahmi KS, Alrawi A. Dermatofibrosarcoma Protuberans: Insights into a Rare Soft Tissue Tumor. J Clin Imaging Sci. 2016;6:16. (PMID: 27195182)
 Bradley J. Carra, Liem T. Bui-Mansfield, Seth D. O'Brien, and Dillon C. Chen: Sonography of Musculoskeletal Soft-Tissue Masses: Techniques, Pearls, and Pitfalls. American Journal of Roentgenology. 2014; 202:6, 1281-1290. (PMID: 24848826)
 Malkud S, Dyavannanavar V. Dermatofibrosarcoma Protuberans. Indian Dermatol Online J. 2017;8(6):495-497. (PMID: 29204401)
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