Dermatofibrosarcoma protuberans: Epidemiology, pathogenesis, clinical presentation, diagnosis, and staging

INTRODUCTION — Dermatofibrosarcoma protuberans (DFSP) is an uncommon locally aggressive cutaneous soft tissue sarcoma. Approximately 85 to 90 percent of DFSPs are low grade, while the remainder contain a high-grade sarcomatous component (which is usually a fibrosarcoma, designated DFSP-FS) and are considered to be intermediate-grade sarcomas [1]. Although they rarely metastasize (fewer than 5 percent of cases), all DFSP variants have a propensity to recur locally. Recurrence potential is directly related to the extent of resection. (See "Dermatofibrosarcoma protuberans: Treatment", section on 'Importance of resection margins'.)

This topic review will focus on the epidemiology, molecular pathogenesis, histology, clinical presentation, diagnosis, and staging of DFSP. Treatment of DFSP and issues specific to DFSP arising in the head and neck region are discussed in detail elsewhere. (See "Dermatofibrosarcoma protuberans: Treatment" and "Head and neck sarcomas", section on 'Desmoids and dermatofibrosarcoma protuberans'.)

EPIDEMIOLOGY — Dermatofibrosarcoma protuberans (DFSP) is a relatively rare tumor. Estimates of the overall incidence of DFSP in the United States are 0.8 to 4.5 cases per million persons per year [2-4]. In the United States, DFSP accounts for between 1 and 6 percent of all soft tissue sarcomas [5,6] and 18 percent of all cutaneous soft tissue sarcomas [3]. In a series of 12,114 cutaneous soft tissue sarcomas derived from the Surveillance, Epidemiology and End Results (SEER) tumor registry from 1992 through 2004, DFSP was second only to Kaposi sarcoma, which accounted for 71 percent of cases [3].

The Bednar or pigmented variant (distinguished by the dispersal of melanin-containing cells in an otherwise typical DFSP) is even less common. It represents fewer than 5 percent of all DFSP cases and is more common in Black individuals [4,7-10]. The fibrosarcomatous variant of DFSP (DFSP-FS) accounts for approximately 5 to 15 percent of DFSPs [11,12].

DFSP most often arises in adults in their thirties [1,4,13-15], but it has been described in all age groups including children and older adults; rarely it presents congenitally [1,4,8,14,16-18]. In one large series, children accounted for 6 percent of all cases of DFSP [19]. The so-called giant cell fibroblastoma is considered to be the juvenile form of DFSP, given its similar morphology, identical chromosomal translocation, and CD34 positivity [20-22]. (See 'Molecular diagnostics' below and 'Immunohistochemistry (IHC)' below.)

In some reports, patients with DFSP-FS are older at presentation (median age 56 versus 37 years [23]). (See 'Fibrosarcomatous variant' below.)

DFSP is found in similar frequencies in males and females, although some large series suggest a slight male predominance [1,24-27]. DFSP is more common in Black individuals than in White individuals (eg, 7.1 versus 3.6 per million in the SEER registry series described above [4]).

MOLECULAR PATHOGENESIS — Over 90 percent of dermatofibrosarcoma protuberans (DFSPs) are characterized by a unique translocation t(17;22) (q22;q13) [28-32]. This translocation usually results in the formation of supernumerary ring chromosomes, which are derived from chromosome 22 and contain low level amplified sequences from 17q22-qter and 22q10-q13.1. Less common, a linear derivative of chromosome 22 (linear der[22]) results, which is most often unbalanced.

Both the ring chromosomes and the translocated linear der(22) contain a unique fusion gene in which the gene for platelet-derived growth factor beta polypeptide (PDGFB gene) is fused with the highly expressed collagen type 1A1 (COL1A1) gene [33,34]. This places expression of the normally inhibited PDGFB gene under the activating control of the COL1A1 promoter. The resulting PDGFB/COL1A1 fusion protein is processed to produce fully functional PDGFB, which results in continuous autocrine activation of the platelet-derived growth factor receptor b (PDGFRb), a tyrosine kinase [35-37]. This molecular alteration, which has been demonstrated in over 90 percent of DFSPs, is thought to be fundamental to the development of the tumor [6,35,38,39].

To date, 34 different PDGFB/COL1A1 fusion variants have been described; the break point in PDGFB is constant, whereas in COL1A1, the break may occur in any of the exons coding the alpha-helical region (codons 6 to 49) [6]. There appears to be no association between the different variants of the PDGFB/COL1A1 fusion gene and the histopathologic subtype or clinical characteristics [40].

In most of the reported cases of DFSP in which t(17;22) has not been found, an alternative translocation, usually (but not inevitably [41]) involving the PDGFB gene on chromosome 22, has been detected [42-44].

Highly sensitive fluorescence in situ hybridization (FISH) assays have been developed to detect the PDGFB/COL1A1 fusion transcript, the presence of which can be useful diagnostically [38]. (See 'Molecular diagnostics' below.)

In addition, the constitutive activation of the tyrosine kinase receptor PDGFRb by the PDGFB/COL1A1 fusion transcript in the majority of cases provides the rationale for targeted inhibition of this pathway as a potential treatment strategy. (See "Dermatofibrosarcoma protuberans: Treatment", section on 'Molecularly targeted therapy'.)

Fibrosarcomatous variant — The fibrosarcomatous variant of DFSP (DFSP-FS) is also characterized by a high frequency of t(17;22), which supports the theory of common histogenesis of both the DFSP and the fibrosarcomatous tissue [26,45]. In some cases, the clonal evolution from DFSP to a DFSP-FS (or less commonly, DFSP with areas of pleomorphic sarcoma) involves genomic gains in the PDGFB/COL1A1 fusion gene [11,37,46,47]. These results suggest a role for the PDGFB/COL1A1 fusion protein in sarcomatous change in DFSP over time.

However, this is not a universal finding. Others describe the early development of microsatellite instability (MSI) and the later acquisition of TP53 mutations in cases with a high-grade sarcoma component [11,48-50]. As an example, Japanese investigators analyzed MSI and TP53 mutations in 44 tumors from 36 patients with either DFSP (n = 27) or DFSP-FS (n = 9) [48]. A high rate of MSI occurred significantly more often in DFSP-FS compared with DFSP (4 of 9 versus 1 of 27 patients). Mutational analysis revealed 10 TP53 point mutations in six patients, four of which were missense mutations and six silent. Three of the four missense mutations were found in the DFSP-FS group compared with only one in the DFSP group. These results suggest that a different molecular pathophysiology underlies the acquisition of high-grade sarcomatous change.

CLINICAL PRESENTATION — In its earliest stage, dermatofibrosarcoma protuberans (DFSP) most commonly presents as an asymptomatic, indurated plaque that slowly enlarges over months to years. The tumors are covered by skin-colored, brown-yellow, red-tinged, sclerodermiform, or telangiectatic atrophic skin. Early lesions may be violet-red or blue at the margins. The Bednar pigmented variant typically contains brown pigmentation and has an irregular surface [7,9]. Less common, DFSP presents as a firm cutaneous nodule.

As the tumor slowly enlarges, it becomes raised, firm, and nodular; the surrounding skin may be telangiectatic [13]. The nodule is often fixed to the dermis but moves freely over deeper tissues. Fixation to deeper structures is observed late in the course of the disease [13]. Once nodules appear, growth is often accelerated, and the tumor may ulcerate, bleed, or become painful. Untreated, DFSP can attain massive dimensions, producing the large "protuberant" nodules for which the disease is named. However, at the time of diagnosis, most tumors are superficial (77 percent in one series of 159 patients [1]) and less than 5 cm in diameter (84 percent in the same series [1]).

The most common location for a DFSP is on the trunk and proximal extremities, generally on the chest and shoulders [4,24,27,51]. The following site distribution was observed in a series of 6,817 patients reported to the Surveillance, Epidemiology, and End Results (SEER) database between 2000 and 2010 [4]:

●Trunk – 42 percent

●Lower extremity – 21 percent

●Upper extremity – 21 percent

●Head and neck – 13 percent

●Genitals – 1 percent

Rarely, DFSP arises within a preexisting scar (including a vaccination scar) or tattoo [9,52-55]. Most DFSPs arise from the dermis; however, they may also arise in the subcutaneous tissues, sometimes as a mass in the breast [56,57] or on the head [58].

The majority of DFSPs exhibit an indolent growth pattern, and in most cases, the lesion has been present for years [13,59]. Indolent growth, coupled with the rarity of DFSP and the variability in clinical appearance, contributes to diagnostic delay. As is seen with desmoid tumors, accelerated growth may occur during pregnancy [60,61]. (See "Desmoid tumors: Epidemiology, molecular pathogenesis, clinical presentation, diagnosis, and local therapy".)

The clinical signs and symptoms associated with the fibrosarcomatous variant of DFSP (DFSP-FS) are similar to those of classic DFSP, and even though DFSP-FS tends to be larger and present for a longer period of time than conventional DFSP [26], neither history nor physical examination is helpful in recognizing the presence of a sarcomatous component.

Metastatic disease — Metastases to regional lymph nodes are extremely rare, with only a few case reports in the literature [27,62]. Distant hematogenous metastases are even rarer and are most likely in patients who have had multiple local recurrences after inadequate surgical resection [25]. 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 brain, bone, and other soft tissues are reported. Although some authors report a rate of metastases as high as 5 percent, it is probably closer to 1 percent for classic (low-grade) DFSP [25,27,63].

DIAGNOSIS — Dermatofibrosarcoma protuberans (DFSP) should be suspected in any patient with a history of a firm, slow-growing cutaneous nodule. Findings on dermoscopy (epiluminescence microscopy) can help to suspect DFSP [64], but definitive diagnosis requires a core needle or incisional biopsy. For de novo previously untreated tumors, fine needle aspirate (FNA) biopsy does not satisfactorily provide enough tissue to render an accurate diagnosis [65,66]. However, FNA may be useful to establish the diagnosis of recurrent disease in a previously treated patient [66].

Histology — Histologically, DFSP is composed of monomorphic, benign-appearing (low mitotic activity) spindle cells arranged in an irregularly whorled or storiform pattern said to resemble a straw mat [67]. The cells intersect in tight right angles around central vessels, and early lesions may have a narrow tumor-free zone (Grenz Zone) between the tumor and epidermis [13]. A predominant histologic characteristic of DFSP is its capacity to invade surrounding tissues to a considerable distance from the central focus of the tumor, with tumor cells invading subcutaneous tissue in the form of irregular tentacle-like projections through the septa and fat lobules [6]. These peripheral tumor extensions may have a bland appearance with few tumor cells, and at first glance, they can appear similar to normal fibrous tracts. This feature makes it difficult to determine the true border of the lesion. This is why local recurrences are frequent after excision with an apparently wide margin.

As noted above, an uncommon variant is the Bednar tumor, in which there are melanin-containing dendritic cells interspersed among the spindle cells [6-9]. Other variants are myxoid DFSP with prominent myxoid stromal changes and a multinodular growth pattern with numerous blood vessels, which may be difficult to differentiate from a myxoid liposarcoma [68-70]. Other described variants include sclerosing DFSP and the atrophic type of DFSP [2,6,8,71].

Between 10 and 20 percent of tumors contain a high-grade sarcomatous component that is usually, but not inevitably [27], a fibrosarcoma (hence the abbreviation DFSP-FS) [1,6,72-74]. The sarcomatous component typically occupies between 20 and 80 percent of the tumor (median, 60 percent) [74]. The spindle cells in the sarcomatous areas show marked cellular and nuclear pleomorphism, and the mitotic rate is usually (but not always) higher than in the typical DFSP component [74]. Upon immunohistochemical staining (IHC), staining for CD34 is often lost in the sarcomatous component. (See 'Immunohistochemistry (IHC)' below.)

Sarcomatous change of a DFSP is a form of tumor progression. The presence of a sarcomatous component increases the tumor grade from low to intermediate, but the impact on overall prognosis is debated. Most but not all series suggest a higher rate of metastases and a worse prognosis in these patients. The impact of a sarcomatous component on local recurrence rates (especially in patients who undergo optimal surgery) is even less clear; at least some of the discrepancy in reported results reflects the adequacy of surgical excision rather than a true difference in local aggressiveness of the DFSP-FS variant. These issues are discussed in detail elsewhere. (See "Dermatofibrosarcoma protuberans: Treatment", section on 'Prognosis'.)

In most cases, examination of a hematoxylin and eosin-stained specimen by light microscopy provides an unequivocal diagnosis of DFSP. However, it may be difficult to distinguish DFSP histologically from other mesenchymal neoplasms such as a dermatofibroma (the fibrous type of benign fibrous histiocytoma), fibromatosis (desmoid tumor), fibrosarcoma, leiomyosarcoma, undifferentiated/unclassified soft tissue sarcoma (formerly known as malignant fibrous histiocytoma or undifferentiated pleomorphic sarcoma), or atypical fibroxanthoma. In such cases, IHC or even molecular diagnostic testing for the characteristic fusion gene may be helpful. Updated guidelines for management of DFSP from the National Comprehensive Cancer Network (NCCN) [75] recommend appropriate and confirmatory immunostaining in all cases of suspected DFSP. (See 'Molecular pathogenesis' above.)

Immunohistochemistry (IHC) — DFSP usually stains positively for CD34, hyaluronate, and vimentin, and negatively for factor XIIIa (table 1) [2,6,67,76,77]. CD34 is one of the most useful stains to differentiate DFSP from dermatofibroma and other soft tissue tumors. The spindle cells of DFSP stain positively with CD34, while dermatofibromas are usually CD34-negative. In fact, the finding of CD34 positivity has renewed the debate over the cellular origins of DFSP. (See 'Implications of IHC for histogenesis' below.)

Unfortunately, the reliability of CD34 staining is not absolute. The sensitivity of CD34 IHC in DFSP ranges from 84 to 100 percent [67,76-78], while between 2.5 and 5 percent of dermatofibromas stain positively [67,78]. There are also reports of loss of CD34 expression with the transition of DFSP to DFSP-FS and in myxoid DFSP [6,74,79].

A more recent study suggests utility for IHC staining for hyaluronate (the major component of extracellular matrix) and CD44 (a membrane glycoprotein thought to be its cell surface receptor) in the differential diagnosis of dermatofibroma and DFSP. The cells of dermatofibromas tend to stain intensely for CD44, while its stroma stains faintly for hyaluronate [80]. In contrast, DFSP tends to be strongly positive for hyaluronate, while CD44 is significantly reduced or absent.

Additional immunostaining with nestin, apolipoprotein D, and cathepsin K may be considered for equivocal lesions [81-83]; alternatively, FISH (fluorescence in situ hybridization) or PCR (polymerase chain reaction) can be used to identify a characteristic translocation. (See 'Molecular diagnostics' below.)

Implications of IHC for histogenesis — The exact type of dermal mesenchymal cell from which DFSP arises is debated. Until more recently, the histochemical and electron microscopic evidence seemed to point toward a fibroblastic cellular origin, because DFSP cells stain uniformly for vimentin and contain active endoplasmic reticulum that synthesizes collagen [84,85]. However, the finding of CD34 positivity in DFSP has raised the possibility that dendritic cells in the skin may be responsible, possibly those derived from circulating hematopoietic progenitor cells. CD34 is a surface antigen that is expressed on normal hematopoietic stem cells that seems to be involved in the process of leukocyte adhesion to the vascular endothelium and in the control of immune responses. (See "Overview of hematopoietic stem cells".)

IHC staining characteristics suggest that in normal skin, there appear to be at least three different kinds of dermal mesenchymal cells, other than endothelial cells [86]:

●CD34-negative/factor XIIIa-negative, as in the majority of fibroblasts in the reticular dermis

●CD34-negative/factor XIIIa-positive, as in dermatofibromas

●CD34-positive/factor XIIIa-negative, as in DFSP

In normal skin, the CD34-positive cells are a distinct population of spindle-shaped cells that are present in a perivascular, perifollicular, and peri-sweat gland distribution, and on interstitial dermal and subcutaneous dendritic cells. It is speculated that these dendritic cells might directly evolve from circulating hematopoietic progenitor cells that have become skin-associated and that they represent the cell of origin of DFSP [87]. This is an area of ongoing investigation.

Molecular diagnostics — As noted above, over 90 percent of cases of DFSP have a characteristic unbalanced translocation t(17;22) that places the PDGFB gene under the control of the COL1A1 promoter. The fusion transcript of this chimeric gene can be identified using reverse transcription polymerase chain reaction (RT-PCR) or fluorescence in situ hybridization (FISH). Both techniques were compared on a study of 103 archival DFSPs; although both techniques had a similar specificity (100 percent), FISH was more sensitive than RT-PCR for detection of the PDGFB/COL1A1 transcript (90 versus 72 percent) [32].

Routine molecular testing is not needed in all cases. Molecular testing should be used if the diagnosis is in doubt or to predict the likelihood of response to the tyrosine kinase inhibitor imatinib [88]. The multicenter GENSARC study, conducted in 32 French sarcoma centers found that molecular diagnostics altered the diagnosis in only 5 of 50 patients with DFSP (10 percent) when cases were reviewed by an expert group of pathologists [89]. (See 'Molecular pathogenesis' above and "Dermatofibrosarcoma protuberans: Treatment", section on 'Treatment of locally advanced, recurrent, and metastatic disease'.)

DIFFERENTIAL DIAGNOSIS — The clinical differential diagnosis of dermatofibrosarcoma protuberans (DFSP) is broad, and can include a number of diseases, depending on the size and location of the tumor. The nodular form of DFSP may be clinically confused with neurofibroma, leiomyoma, epidermal (sebaceous) cyst, malignant melanoma, basal cell carcinoma, keloid, desmoid tumor, dermatofibroma, lipoma, nodular fasciitis, sarcoidosis, and other cutaneous soft tissue sarcomas including Kaposi sarcoma, fibrosarcoma/fibromyxosarcoma, liposarcoma, leiomyosarcoma, angiosarcoma, and undifferentiated/unclassified soft tissue sarcoma (previously known as malignant fibrous histiocytoma, or undifferentiated pleomorphic sarcoma). (See "Overview of benign lesions of the skin" and "Classic Kaposi sarcoma: Clinical features, staging, diagnosis, and treatment" and "AIDS-related Kaposi sarcoma: Clinical manifestations and diagnosis" and "Ganglion cysts of the wrist and hand" and "Desmoid tumors: Epidemiology, molecular pathogenesis, clinical presentation, diagnosis, and local therapy" and "Keloids and hypertrophic scars" and "Basal cell carcinoma: Epidemiology, pathogenesis, clinical features, and diagnosis" and "Overview of soft tissue musculoskeletal disorders" and "Melanoma: Clinical features and diagnosis" and "Clinical manifestations and diagnosis of sarcoidosis" and "Clinical presentation, histopathology, diagnostic evaluation, and staging of soft tissue sarcoma".)

The plaque and atrophic forms of DFSP may clinically resemble morphea (localized scleroderma), morpheaform basal cell carcinoma, anetoderma (loss of normal elastic tissue sometimes seen with systemic lupus erythematosus or antiphospholipid syndrome), or scar [90,91]. (See "Pathogenesis, clinical manifestations, and diagnosis of morphea (localized scleroderma) in adults" and "Basal cell carcinoma: Epidemiology, pathogenesis, clinical features, and diagnosis", section on 'Morpheaform/infiltrative' and "Clinical manifestations of antiphospholipid syndrome".)

STAGING SYSTEM — There is no uniformly used staging system for dermatofibrosarcoma protuberans (DFSP); three are in use:

●As with other soft tissue sarcomas, many clinicians stage DFSP and the fibrosarcomatous variant of DFSP (DFSP-FS) according to the American Musculoskeletal Tumor Society (MSTS) staging system, which is based on histologic grade (using a two-tiered system, low versus high) and whether the tumor is confined to an anatomic compartment (table 2) [92]. All DFSP fall into the category of stage IA or IB disease. The designation of stage II disease in the MSTS staging system implies high-grade histology and does not apply to DFSP or DFSP-FS.

●There is an American Joint Committee on Cancer (AJCC)/ Union for international Cancer Control (UICC) staging system for soft tissue sarcomas that includes DFSP. The most recent version (eighth edition, 2017) provides a separate classification system for tumors of the extremities and trunk (table 3) and those arising in the head and neck (table 4) [93,94]. (See "Clinical presentation, histopathology, diagnostic evaluation, and staging of soft tissue sarcoma", section on 'Staging'.)

●In Germany, a staging system was described (the Short German Guidelines for DFSP), but the clinical utility is unclear, as the vast majority of tumors fall into the stage I category [95]:

•Stage I – Local tumor involvement

•Stage II – Lymph node metastases

•Stage III – Distant metastases

STAGING EVALUATION — Most dermatofibrosarcoma protuberans (DFSPs) are superficial, and tumor extent and mobility as well as regional node assessment can be assessed by physical examination. Because a characteristic of DFSP is asymmetric growth and frequent finger-like extensions, determining tumor size and extent of penetration into surrounding tissues is of utmost importance, and special attention should be given to palpation around the tumor and regional lymph nodes. The history, physical examination, and review of systems largely determine the extent of workup that is required.

The physical examination should include a complete skin examination. Imaging studies are not required in every case of DFSP, but can be helpful in select cases (large or recurrent tumors, suspicion of bone invasion) to define the extent of disease.

For purposes of treatment planning, magnetic resonance imaging (MRI) is useful to determine the deep extent of the tumor, particularly with large or recurrent lesions at sites other than the head and neck or upper thorax; it is more sensitive than palpation for ascertaining the depth of invasion [16,96,97]. On conventional T1-weighted images, DFSP can be isointense, hypointense, or hyperintense compared with normal skeletal muscle and typically has a lower signal intensity than subcutaneous fat [96]. On T2-weighted images, there may be higher signal intensity as compared with fat, or an intermediate signal intensity that is similar to fat.

Computed tomography (CT) scanning is not indicated except if underlying bone involvement is suspected.

Because of the rarity of both lymphatic and hematogenous dissemination, an extensive staging workup is unnecessary unless there are suggestive aspects in the history and physical examination for metastatic disease, if adverse prognostic histologic features are present (eg, fibrosarcomatous transformation), and for recurrent tumors [98]. Although metastases are rare overall, the lungs are the most common site. (See 'Metastatic disease' above.)

Some suggest chest CT to evaluate for lung metastases if the primary lesion is advanced, recurrent, and/or intermediate grade [63]. We usually get a chest radiograph preoperatively in all patients, and we preferentially order chest CT for those with advanced, unfavorable tumors of prolonged duration, recurrent tumors, or if the tumor has sarcomatous transformation (DFSP-FS).

Guidelines for treatment of DFSP from the National Comprehensive Cancer Network (NCCN) [75] do not make any recommendations for imaging of the primary tumor or staging workup.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Soft tissue sarcoma".)

SUMMARY

●Dermatofibrosarcoma protuberans (DFSP) is a rare low- to intermediate-grade cutaneous sarcoma with little metastatic potential but a significant propensity for local recurrence. The recurrence potential is directly related to the extent of resection. (See 'Introduction' above.)

●Over 90 percent of DFSPs have a translocation involving chromosomes 17 and 22, t(17;22). A fusion gene results (platelet-derived growth factor-beta [PDGFB]/collagen type 1A1 [COL1A1]), which causes dysregulated expression of PDGFB and continuous autocrine activation of the platelet-derived growth factor receptor b (PDGFRb), a tyrosine kinase. This provides both a unique molecular diagnostic test for DFSP and the rationale for targeted inhibition of this pathway as a potential treatment strategy. (See 'Molecular pathogenesis' above.)

●DFSP most commonly presents as an asymptomatic, skin-colored indurated plaque that slowly enlarges over months to years. As the tumor slowly enlarges, it becomes raised, firm, and nodular. The most common locations are the trunk and proximal extremities. (See 'Clinical presentation' above.)

●Definitive diagnosis requires a core needle or incisional biopsy. Most of the time, the correct diagnosis can be made by review of hematoxylin and eosin-stained sections, combined with immunohistochemical stating. Molecular testing for the PDGFB/COL1A1 fusion protein may help if the diagnosis is in doubt. (See 'Diagnosis' above.)

●The clinical differential diagnosis of DFSP is broad. DFSP may be clinically confused with neurofibroma, leiomyoma, epidermal cyst, malignant melanoma, morpheaform basal cell carcinoma, keloid, desmoid tumor, Kaposi sarcoma, fibrosarcoma, dermatofibroma, nodular fasciitis, or sarcoidosis. (See 'Differential diagnosis' above.)

●Most clinicians stage DFSP according to the American Musculoskeletal Tumor Society (MSTS) staging system, which is based on histologic grade (using a two-tiered system, low versus high) and whether the tumor is confined to an anatomic compartment (table 2). Most tumors are IA or IB. (See 'Staging system' above.)  

●Imaging studies are not required in every case of DFSP, but magnetic resonance imaging (MRI) can be helpful in defining the extent of disease in cases of a large or recurrent primary tumor. Computed tomography (CT) scanning is not indicated except if underlying bone involvement is suspected. Because of the rarity of both lymphatic and hematogenous dissemination, an extensive staging workup is usually unnecessary in the absence of clinical suspicion for metastatic disease or adverse prognostic histologic features. We usually get a chest radiograph preoperatively in all patients, and we preferentially order chest CT for those with advanced, unfavorable tumors of prolonged duration or if the tumor has sarcomatous transformation (DFSP-FS). (See 'Staging evaluation' above.)