Dermatofibrosarcoma protuberans (DFSP) is a rare, slow-growing, low-grade fibroblastic sarcoma arising from the dermis and subcutaneous tissue. It demonstrates locally aggressive behavior with an infiltrative growth pattern through tentacle-like extensions — this feature is responsible for the high local recurrence rate. Metastasis is rare (1-5%). US is the primary evaluation modality and appears as a dermal/subcutaneous, hypoechoic, irregularly marginated mass. COL1A1-PDGFB gene fusion is the pathognomonic molecular marker.
Age Range
20-60
Peak Age
35
Gender
Equal
Prevalence
Rare
DFSP arises from fibroblast-like cells residing in the dermis. COL1A1-PDGFB gene fusion (t(17;22)(q22;q13) translocation) is present in over 90% of tumors — this fusion enables autocrine overproduction of PDGFB (platelet-derived growth factor B) protein and tumor cells produce their own growth signals. This autocrine stimulation is the fundamental mechanism of the infiltrative growth pattern. Tumor cells arrange in storiform (cartwheel) pattern and send tentacle-like extensions into surrounding tissue — these extensions spread through dermis, subcutaneous fat, and even muscle tissue. The hypoechoic appearance on US results from dense and homogeneous packing of tumor cells — fibroblast cells create a homogeneous tissue with low acoustic impedance. Irregular margins reflect the disruption of surrounding tissue interfaces by tentacle-like extensions. The efficacy of imatinib treatment is directly based on blockade of the PDGFB-autocrine loop.
Thin hypoechoic tentacle-like extensions from the main mass into subcutaneous fat tissue are the signature finding of DFSP. This infiltrative growth pattern is critical for surgical margin planning — wide surgical margin (≥3cm) or Mohs micrographic surgery is required.
On US, DFSP appears as a homogeneous or mildly heterogeneous hypoechoic solid mass bridging dermis and subcutaneous tissue. Margins are irregular and indistinct — tentacle-like extensions prevent formation of a definite boundary with surrounding tissue. The mass is usually ovoid or plaque-like in shape. Overlying skin may be thickened. The dermis-subcutaneous boundary is disrupted due to DFSP.
Report Sentence
A hypoechoic solid mass bridging dermis and subcutaneous tissue with irregular margins is seen; DFSP should be considered in the differential diagnosis.
High-resolution US can demonstrate tentacle-like extensions of DFSP extending into subcutaneous fat tissue. These extensions appear as thin hypoechoic bands radiating from the main mass and infiltrate between surrounding fat lobules. This infiltrative pattern is characteristic of DFSP and critically important for surgical margin planning — these macroscopically invisible extensions are the primary cause of positive surgical margins and recurrence.
Report Sentence
Tentacle-like hypoechoic extensions from the main mass infiltrating between subcutaneous fat lobules are identified, consistent with the infiltrative growth pattern of DFSP.
On color and power Doppler, DFSP shows mild-to-moderate internal vascularity. Vascularity pattern may be regular or slightly irregular. Arterial and venous flow components are detected. Marked hypervascularity is not seen — reflecting low-grade sarcoma behavior. This finding has discriminating value from completely avascular benign dermatofibroma.
Report Sentence
Mild-to-moderate vascularity is identified within the mass on color Doppler, consistent with low-grade solid tumor.
On MRI T2, DFSP appears as a hyperintense, homogeneous or mildly heterogeneous mass. It shows extension between dermis and subcutaneous tissue and tentacle-like extensions may be visible as bright bands on T2. Surrounding tissue edema may be mild. Muscle invasion may be seen in advanced cases.
Report Sentence
A hyperintense mass extending between dermis and subcutaneous tissue is seen on T2, with infiltrative extensions consistent with DFSP.
On contrast-enhanced MRI, DFSP shows moderate homogeneous enhancement. Tentacle-like extensions may also show enhancement — this feature helps with surgical margin planning. Necrosis areas are generally absent (low-grade tumor).
Report Sentence
The mass shows moderate homogeneous enhancement on post-contrast sequences with enhancing extensions noted beyond the main mass.
High-resolution US can demonstrate that DFSP arises from the dermis — the tumor shows continuity with the dermis and the dermal-subcutaneous interface is disrupted. This dermal origin is important in distinguishing DFSP from subcutaneous tumors. The normal echogenicity of overlying skin may be disrupted.
Report Sentence
The mass shows continuity with the dermis and the dermal-subcutaneous interface is disrupted, consistent with a dermal-origin tumor (DFSP).
Criteria
Spindle cell proliferation in storiform pattern, CD34+, COL1A1-PDGFB fusion+
Distinct Features
Most common type (80-90%). Low-grade, locally aggressive, metastasis rare. Treatment is wide excision.
Criteria
High-grade fibrosarcoma area in DFSP background, increased mitotic activity, may show CD34 loss
Distinct Features
Increased metastasis risk (15-20%). More aggressive biological behavior. Heterogeneous US appearance. Adjuvant therapy should be considered.
Criteria
Dendritic cells containing melanin pigment in DFSP stroma
Distinct Features
Rare variant (1-5%). May clinically resemble melanoma. Prognosis similar to classic DFSP.
Distinguishing Feature
Fibromatosis is fascia-associated and fusiform-shaped, DFSP is dermal-origin and shows tentacle-like extensions. Fibromatosis is more homogeneous and less vascular.
Distinguishing Feature
Hematoma is avascular and shows time-dependent echogenicity change. DFSP is vascular and shows stable appearance.
Distinguishing Feature
Giant cell tumor is peritendinous and associated with tendon sheath. DFSP is dermal-origin with no tendon association.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
6-monthBiopsy should confirm diagnosis in suspected DFSP. Treatment is wide surgical resection (≥3cm margin) or Mohs micrographic surgery — local recurrence rate may reach 20-50% with narrow margins. Imatinib (PDGFR inhibitor) is effective in inoperable or metastatic cases. Follow-up with clinical examination + US at 6-month intervals for first 3 years, then annually.
DFSP is a low-grade sarcoma with metastatic risk less than 5%. However, due to infiltrative growth, wide surgical margins (2-3 cm) with Mohs micrographic surgery or wide excision are required. Local recurrence rate is 20-50% with inadequate margins. Imatinib (tyrosine kinase inhibitor) is effective in inoperable or metastatic cases.