Different sonographic presentations of dermatofibrosarcoma protuberans

Abstract

Backround

Dermatofibrosarcoma protuberans (DFSP) is a low-grade spindle cell sarcoma of fibroblastic origin. This tumor originates in the dermis and infiltrates the subcutaneous tissue. The highest incidence occurs in the third and fourth decades of life, affecting most frequently the trunk and proximal extremities. Ultrasound is performed in those cases where the clinical appearance of the lesion is not typical and when the physician wants to determine the extent and depth of the lesion.

Material and methods

Retrospective analysis of the ultrasound and demographic findings of thirteen patients with DFSP.

Results

13 patients, 8 females and 5 males, aged from 2 months to 58 years old. One patient with two different separated synchronous tumors. On ultrasonography they compromised the dermal hypodermal layers in 93% of the cases and 1 dermal lesion. The compromise reached the aponeurotic plane in two cases. The sized varied from 5 to 38 mm. They presented as a well-defined hypoechogenic nodule in seven cases (50%). In three cases (21%) they presented as a hypoechogenic infiltrate ill-defined border solid lesion; in two cases as a plaque ill-defined lesion, and two cases as a pseudonodular inflammatory lesion with irregular borders. All lesions appeared vascularized on color Doppler imaging.

Conclusion

DFSP is a low grade sarcoma of fibroblastic origin, that usually arises in the dermis and infiltrates the subcutaneous tissue. The clinical presentations are variable. On ultrasound we found different patterns: well-defined hypoechogenic solid nodule, hypoechogenic infiltrate ill-defined border solid lesion, plaque ill-defined lesion, and pseudonodular inflammatory lesion. It is important to know and recognize this suspicious different ultrasound presentations in order to recommend a histological study.

Introduction

Dermatofibrosarcoma protuberans (DFSP) is a low-grade spindle cell sarcoma of fibroblastic origin. It represents less than 0.1% of all malignant neoplasms and about 6% of all soft tissue sarcomas, however it is the most common primary sarcoma of the subcutaneous tissue (1, 2). The incidence of distant metastases is less than 5%, but the recurrence rate is up to 60%. (2).

The highest incidence of DFSP occurs in the third and fourth decades of life. It most commonly affects the trunk (50–60%) and proximal extremities (20–30%), but it can present in any part of the body (1, 2).

DFSP is a slow-growing mesenchymal tumor that usually originates in the dermis and is generally associated with typical clinical features (1, 3). Clinically, DFSP begins as a small, progressively enlarging, erythematous or bluish nodule that protrudes from the skin and may eventually ulcerate. (1).

Ultrasound (US) is usually performed in those cases where the clinical appearance of the lesion is not typical and when the physician wants to determine the extent and depth of the lesion. (1).

The standard treatment for DFSP remains surgical resection with peripherical and deep.margin control (4).

Material and methods

A twelve-year retrospective analysis approved by the Institutional Review Board, who granted a waiver for informed consent. This review was performed for patients referred for a high resolution ultrasound whose records were kept in the small part US database and in the pathology biopsies archives.

Thirteen patients diagnosed with dermatofibrosarcoma protruberans were selected. The inclusion criteria were to have a small part ultrasound images recorded in the computational medical system and histological confirmation.

US examination was performed with Toshiba Aplio i800 and Philips (Epiq model) equipment, using linear high-resolution transducer (24–5 MHz, 18–5 MHz and 17–5 MHz), in the majority of cases, a gel pad was used. All the examinations were performed by ultrasound radiologists.

The ultrasound images were retrieved from PACS (Agfa IMPAX ®).

Sex and age distribution, location, size, and sonographic findings were analyzed retrospectively by two ultrasound radiologists who provided a consensus appraisal of these findings. The cutaneous layers, size and ultrasound characteristics were analyzed.

Results

The group consisted of 13 patients, 8 females and 5 males.

The age distribution was from 2 months to 58 years old. Three pediatric patients aged from 2 months to 9 years old, The adult group was from 33 to 58 years old, with a mean age of 54 years. All the adult patients were from the third to fifth decades of life. Three patients between 30–39 years old, three patients between 40–49 years old and four patients between 50–59 years old.

The clinical presentation in the pediatric group was as a vascular anomaly in two cases and as a nodule in one case.

In the adult form, the clinical diagnoses were cutaneous cysts ( 4 cases), tumor ( 2 cases) dermatofibroma ( 2 cases), morphea ( 1 case), nodule ( 1case).

The locations of the lesions were: lower extremities (5 cases), thoraco-abdominal wall (5cases), head and scalp (2 cases) and upper extremity (1 case).

One patient had two separated synchronous lesions on the lower extremity, both DFSP, and for the analysis we considered 14 lesions.

On the ultrasonographic findings, the lesions compromised the dermal hypodermal layers in 93% of the cases ( 13 lesions) and just 1 dermal lesion ( Fig. 1). In some cases, the compromise of the subcutaneous tissue crossed the fascia reaching the aponeurotic plane (2 cases).

Fig. 1.

Anterior aspect of the right thigh US. Solid hypoechogenic well-defined dermal lesion. Adequate dermo-hypodermic interface

The size varied from 5 to 38 mm in the diameter parallel to the skin surface and the depth from 1.2 mm to 18 mm. Two lesions measured less than 10 mm, six lesions measured from 10 – 20 mm, and six lesions were bigger than 20 mm.

They presented as a well-defined hypoechogenic nodule in seven cases (50%) (Fig. 2,3). In three cases (21%) as a hypoechogenic infiltrate ill-defined border solid lesion (Fig. 4), in two cases as a plaque ill-defined lesions (Fig. 5), and in two cases as a pseudonodular inflammatory lesion with irregular borders. (Fig. 6)(Fig. 7).

Fig. 2.

Left ankle US. Solid, oval hypoechogenic, homogeneous well-defined nodule. It compromises the dermis and subcutaneous tissue. There is a slight increase in the echogenicity of the surrounding subcutaneous tissue. The surface is preserved

Fig. 3.

Medial region ankle US. Solid, oval nodule, located in the dermal and subcutaneous cellular tissue. It presents moderate vascularization on color Doppler

Fig. 4.

Left inguinal region US. Solid infiltrating hypoechogenic lesion, with irregular borders. It comprises the dermo hypodermal layer with extension to the aponeurotic plane

Fig. 5.

Inframammary region US. Superficial hypoechogenic solid plaque, with thinning and mild focal depression of the dermis. It presents irregular contours, with blurring of the dermal-hypodermal interface and a slight focal increase in the echogenicity of the underlying subcutaneous adipose tissue

Fig. 6.

Right posterior thoracic region US. Irregular heterogenous dermo hypodermal lesion with ill-defined borders and increased echogenicity of the adipose tissue looking as pseudo inflammatory lesion

Fig. 7.

Schematic drawing of the different patterns of DFSP on US

On Doppler color imaging and Superb Microvascular imaging ( SMI) all the cases presented vessels inside the lesions. Eight cases (57%) had several vessels inside the lesion with a moderate vascular density and the other 6 cases looked hypovascular, with small isolated vessels inside the lesions.(Fig. 8).

Fig. 8.

Anterior aspect of the right leg US. Pseudonodular heterogeneous, partially defined lesion with important inner vessels on Doppler color (Superb microvascular imaging)

In the pediatric group the presentation as a hypoechogenic nodule was predominant.

In all cases, the histological diagnosis was a dermatofibrosarcoma protuberans.

Discussion

DFSP is a low grade sarcoma of fibroblastic origin, which usually arises in the dermis and infiltrates the subcutaneous tissue. On rare occasions, it can arise de novo in the subcutaneous tissue without dermal involvement (1). It is most commonly seen on the trunk (approximately 50%), the scalp, the breast, and the proximal extremities (5). DFSP typically presents between the ages of 10 and 40, being slightly more common in men. (1, 6) The size of the tumor varies from 1 cm to more than 25 cm, with a mean size of about 4 cm. The infiltration of the dermis tends to be asymmetric with horizontal or vertical frond-like extension into the subcutaneous fat. On rare occasions, the tumor can penetrate the muscular fascia and extend to subfascial tissues (1, 6). Rarely, DFSP can also appear de novo from deeper structures such as muscles (1).

Histologically, DFSP is classified as a fibrohistiocytic tumor of intermediate malignancy. DFSP is composed of relatively uniform, spindle-shaped tumor cells arranged in a predominantly storiform growth pattern and infiltrating the dermis and subcutis in a characteristic diffuse honeycomb fashion (5) In addition to classical DFSP, a number of variants are known and awareness of the latter is important to avoid misdiagnosis of more or less aggressive neoplasms. Morphological variants include pigmented DFSP, fibrosarcomatous DFSP characterized clinically by a more aggressive behavior, DFSP with focal myogenic differentiation, granular cell DFSP, flat atrophic DFSP and myxoid DFSP (5). Focal sarcomatous change is seen in about one-tenth of tumors, mostly fibrosarcoma-like, though occasionally malignant fibrous histiocytoma, with increased risk of sarcomatous transformation in DFSP cases arise from deep tissues (1). Dermatofibrosarcoma protuberans can be safely distinguished from other similar neoplasms of mesenchymal origin based on the immunohistochemical expression of CD34 antigen and the genetic presence of specific chromosomal translocations (7).

Clinically, DFSP begins as a small nodule that slowly grows into a medium-sized, erythematous or bluish, raised lesion that may eventually ulcerate. Given this slow tumor growth, patients often consult a doctor several years after initial appearance (1). DFSP can also present as an asymptomatic purple or pink plaque with a history of slow but persistent growth (8). They are described as three different clinical presentations for DFSP: morphea-like, atrophoderma-like and angioma-like. In our experience in the pediatric cases they presented as a vascular anomaly, but in adults the clinical diagnosis varied from complicated cutaneous cysts, tumor, dermatofibroma and morphea. In this group the age of presentation included pediatric and adult population. Thirty-eight percent of the lesions were present in the lower extremities and 38% on the toracoabdominal wall.

DFSP should be treated surgically with peripherical and deep margin control (4). If the tumor is close to the fascia, it should be excised en-bloc with the tumor to minimize the chance of recurrence. Despite its sarcomatous potential, the tumor has a very good prognosis with a low risk of local recurrence when resection is completed with wide-margin surgery. The likelihood of local recurrence after performing this procedure is performed is less than 10% (1, 9). The experience with Mohs and Breuninger surgery indicates that this procedure is associated with a high probability of cure, provided that the final margins are negative. In contrast, the risk of local recurrence exceeds 50% when the final margins are positive (9). It is very important to have a clear pathological margin and also to well-adjust the requirement of reconstruction, the free margin and the surgical morbidity.

Metastasis is rare and is only seen when there is transformation of the primary tumor into a fibrosarcoma (1).

Most DFSPs are diagnosed clinically. Imaging has been requested in cases of uncertainty regarding the clinical nature of the mass or the need to assess the extent of the tumor. Ultrasound helps to characterize the type of tumor, as well as to evaluate the local infiltration, extension and depth of the tumor.

As in ultrasound of all soft tissue tumors, the diagnosis is made not on the basis of one or two features, but rather on the relative strength of multiple ultrasound features interpreted in conjunction with the clinical presentation. (1) Clearly, not all sonographic features assigned to DFSP will be present in all cases. As DFSP is a tumor with histological variability, as well as different histological subtypes, the ultrasound characteristics are expected to vary. However, based on the described ultrasound features, a DFSP could comfortably be suggested as a possible diagnosis when appropriate and, if necessary, proceed to ultrasound-guided biopsy. The characteristics of DFSP of the breast have also been specifically studied and are similar to those of tumors that occur outside the breast. (6).

In this group, size varied from 5 to 38 mm and the mean size was 20 mm. They presented as a well-defined hypoechogenic nodule in 50% of the cases, in 21% as a hypoechogenic infiltrate ill-defined border solid lesion, in 14% as a plaque ill-defined lesion, and 14% as a pseudonodular inflammatory lesion with irregular borders. This presentation has not been previously reported. On Doppler color imaging and Superb Microvascular imaging (SMI) all the cases had vessels inside the lesions. The pseudonodular inflammatory presentation looks similar to other malignancies such as cutaneous lymphoma.

The differential diagnosis of DFSP includes a subcutaneous neurogenic tumor, fibromatosis, epidermal cyst, vascular malformation, and malignant skin lesions (such as metastatic disease, especially melanoma), and cutaneous lymphoma. Neurogenic tumors tend to be more spindle-shaped, often have thickened nerve segments immediately proximal or distal to the tumor, and have a fairly characteristic echo pattern and vascularization. (10) Vascular malformations typically comprise numerous intercalated vessels with variable echogenic stroma, phleboliths, and moderate compressibility. Malignant skin lesions such as metastases and cutaneous lymphoma are generally more infiltrative than DFSP; however, these can sometimes be differentiated only by biopsy. Also inflammatory lesions can be considered. Thus, it is important to consider DFSP as a differential diagnosis prior to surgery, since wide local excision is necessary to prevent local recurrence.

In most of the cases presented, the clinical diagnosis of DFSP was not made at the time of the ultrasound request, nor was this diagnosis reported as a possibility after the ultrasound (1). The appearances of DFSP on CT and MRI are nonspecific and are helpful in determining the deeper extent of larger lesions (6).

Conclusion

DFSP is a low grade small part sarcoma of fibroblastic origin. The clinical presentations are variable. On ultrasound we found different presentations: well-defined hypoechogenic solid nodule, hypoechogenic infiltrate ill-defined border solid lesion, plaque ill-defined lesion, and pseudonodular inflammatory lesion. It is important to know and recognize this suspicious different ultrasound pattern in order to recommend a histological study.

Funding

This study and all authors have received no funding. No funding was provided for the completion of this study.

Declarations

Conflicts of interest

The authors have nothing to declare.