Dermatofibrosarcoma protuberans (DFSP)^[2] is a rare locally aggressive malignant cutaneous soft-tissue sarcoma. DFSP develops in the connective tissue cells in the middle layer of the skin (dermis).^[3] Estimates of the overall occurrence of DFSP in the United States are 0.8 to 4.5 cases per million persons per year.^[4][5] In the United States, DFSP accounts for between 1 and 6 percent of all soft-tissue sarcomas^[6] and 18 percent of all cutaneous soft-tissue sarcomas. In the Surveillance, Epidemiology and End Results (SEER) tumor registry from 1992 through 2004, DFSP was second only to Kaposi sarcoma.

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Dermatofibrosarcoma protuberans
Other names	DFSP [1]
Histopathological image of dermatofibrosarcoma protuberans. Local recurrence long after the first excision. H&E stain
Specialty	Oncology

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Dermatofibrosarcoma protuberans begins as a minor firm area of skin most commonly about to 1 to 5 cm in diameter. It can resemble a bruise, birthmark, or pimple. It is a slow-growing tumor and is usually found on the torso but can occur anywhere on the body.^[7] About 90% of DFSPs are low-grade sarcomas. About 10% are mixed, containing a high-grade sarcomatous component (DFSP-FS); therefore, they are considered to be intermediate-grade sarcomas. DFSPs rarely lead to a metastasis (fewer than 5% metastasize), but DFSPs can recur locally. DFSPs most often arise in patients who are in their thirties but this may be due to diagnostic delay.

The World Health Organization in 2020 classified the fibro sarcomatous DFSP (DFSP-FS) variant (also termed dermatofibrosarcoma protuberans, fibro sarcomatous) of the dermatofibrosarcoma protuberans as a specific form of the intermediate (rarely metastasizing) fibroblastic and myofibroblastic tumors and other variants of this disorder as a specific form of the intermediate (locally aggressive) fibroblastic and myofibroblastic tumors.^[9]

More than 90% of DFSP tumors have the chromosomal translocation t(17;22). The translocation fuses the collagen gene (COL1A1) with the platelet-derived growth factor (PDGF) gene. The fibroblast, the cell of origin of this tumor, expresses the fusion gene in the belief that it codes for collagen. However, the resulting fusion protein is processed into a mature platelet-derived growth factor which is a potent growth factor. Fibroblasts contain the receptor for this growth factor. Thus the cell "thinks" it is producing a structural protein, but it creates a self-stimulatory growth signal. The cell divides rapidly and tumor forms.

The tissue is often positive for CD34.^[19][20]

DFSP is a malignant tumor diagnosed with a biopsy, when a portion of the tumor is removed for examination. In order to ensure that enough tissue is removed to make an accurate diagnosis, the initial biopsy of a suspected DFSP is usually done with a core needle or a surgical incision.^[21]

Clinical palpation is not entirely reliable for ascertaining the depth of a DFSP infiltration. Magnetic resonance imaging (MRI) is more sensitive addressing the depth of the invasion on some types of DFSP, particularly large or recurring tumors,^[22][23] though MRI is less accurate for identifying infiltration to head and neck tumors.

Due to the rarity, initial presentation of flat plaque (skin hardening) and the slow-growing nature of DFSP, it may be months to years without a protuberance (bump). The dissonance between the name of the neoplasm and its clinical presentations may cause a majority of patients to experience a diagnostic delay. A 2019 research study found out of 214 patients a range between less than a year to 42 years before diagnosis (median, four years) from patients noticing a symptom to diagnosis.^[24]

Currently, a majority of patients (53%) receive a misdiagnosis by health care providers. The most frequent prebiopsy clinical suspicion included cyst (101 [47.2%]), lipoma (30 [14.0%]), and scar (17 [7.9%]).^[24]

It has been suggested an alternative term for DFSP should be dermatofibrosarcoma, often protuberant.^[24]

It is suggested that DFSPs may enlarge more rapidly during pregnancy. Immunohistochemical stains for CD34, S-100 protein, factor XIIIa, and estrogen and progesterone receptors were performed on biopsy specimens. The tumors showed the expression of the progesterone receptor. As with many other stromal neoplasms, DFSPs appear to express low levels of hormone receptors, which may be one factor that accounts for their accelerated growth during pregnancy.^[25]

Treatment is primarily surgical, with chemotherapy and radiation therapy used if clear resection margins are not acquired.^[26]

Distant hematogenous metastases are extremely rare.^[35] Metastases to regional lymph nodes are rarer and are most likely in patients who have had multiple local recurrences after inadequate surgical resection.^[36] Repeatedly recurring tumors have an increased risk for transformation into a more malignant form (DFSP-FS). The lungs are most frequently affected, but metastases to the brain,^[37] bone,^[38] and other soft tissues are reported.

DFSP is not extensively studied due to its rarity and low mortality. The majority of studies are small size case studies or meta-analysis.

The most extensive research study to date was Perspectives of Patients With Dermatofibrosarcoma Protuberans on Diagnostic Delays, Surgical Outcomes, and Nonprotuberance.^[24] The lead researcher, Jerad Gardner, spoke at a TED Talk in February 2020 on the topic.^[39]

R. W. Taylor, in 1890,^[40] first identified DFSP as a keloid sarcoma. Later in 1924, Ferdinand-Jean Darier and Ferrand identified it as a progressive recurrent dermatofibroma. In 1925, E. Hoffmann^[41] coined the term dermatofibrosarcoma protuberans. Bednar tumor was first described by Bednar in 1957.^[42][43]

The following are the ICD-10 medical codes:

• ICD-0: 8832/3^[44] – dermatofibrosarcoma protuberans, NOS
• ICD-0: 8833/3^[44] – pigmented dermatofibrosarcoma protuberans
• ICD-0: 8834/1^[44] – giant cell fibroblastoma
• Fibrosarcomatous dermatofibrosarcoma protuberans: no distinct coding identified

• Subcutaneous tissue infiltration (i.e. "honeycomb" growth pattern)
• Monotonous, plexiform structure of tumour
• DFSP formed both by fibroblastic and histiocytic elements
• Hemosiderin deposits beneath the tumour
• Immunostain positive for CD34

• List of cutaneous conditions