Dermatofibrosarcoma protuberans (DFSP) is a low-grade malignant tumor arising from dermal and subcutaneous tissues and is the most common cutaneous sarcoma (although overall still quite rare). It is most commonly found at the trunk and proximal extremities ⁶.

Its behavior is notable for a high reported local recurrence rate, although outcomes overall are favorable.

Epidemiology

The tumor occurs in patients of all ages, with the highest frequency occurring between ages 20-50 years. Males are slightly more commonly affected than females.

Pathology

It typically arises in the dermis as a multi-nodular mass spreading into the subcutaneous tissues and muscles. Lesions ranging from 1 cm to more than 25 cm have been described in the literature.

Location

The trunk is the most common site of involvement, accounting for almost half of all cases. The extremities, followed by the head and neck, are the next most common sites. 

Patients often ignore these tumors because of their slow growth, and they are often left untreated for many years.

Radiographic features

The typical appearance is that of an unmineralized, round/ovoid/nodular soft-tissue mass involving the skin and subcutaneous adipose tissue. 

Ultrasound

• variable morphology: round/ovoid, lobulated, "tenticle-like projections", and/or irregular ^10,11

• heterogeneous mixed echogenicity or hypoechoic mass ^10,11

• small (<0.5 mm) echogenic foci without comet tail artifact ¹¹

• posterior acoustic enhancement ¹¹

• color Doppler shows low-to-moderate vascularity, more prominent at the periphery than centrally ^10,11

CT

• solitary, mostly well-defined iso- or hypo-dense mass in the subcutaneous tissues ³

• most commonly shows homogeneous enhancement, although rarely heterogeneous enhancement ³

• larger (>5 cm) lesions may show areas of intratumoral non-enhancement, which may indicate necrotic or cystic degeneration within the tumor ³

MRI

• T1: low signal ¹

• T2: ​high signal; usually higher than or equal to adjacent subcutaneous fat ¹

• fat saturation sequences: high signal ¹

• T1 C+ (Gd): enhances ¹

Treatment and prognosis

Dermatofibrosarcoma protuberans has an excellent prognosis after complete resection but has a marked tendency to recur locally if inadequate surgical resection margins are obtained. Metastases are rare, most commonly to the lungs.

Fibrosarcomatous transformation of dermatofibrosarcoma protuberans (FS-DFSP / fibrosarcoma ex-DFSP) is an uncommon and aggressive variant of DFSP, associated with a higher tendency for local recurrence and distant metastasis ^8,9. Wide excision with ≥2 cm margins or Micrographic Mohs surgery with smaller margins is the treatment of choice for FS-DFSP, to avoid local recurrence and metastasis. Radiation has a role in cases with incomplete surgical resection, whereas the PDGFR-inhibitor imatinib is effective in irresectable, locally advanced and metastatic cases ⁸.

History and etymology

It was originally described as a distinct clinicopathologic entity in 1924 by Darier and Ferrand. The term “dermatofibrosarcoma protuberans” was coined by Hoffman in 1925 ³.