Dermatofibrosarcoma protuberans in adolescence : a case report and literature review

Dermatofibrosarcoma protuberans yra itin retas vaikų piktybinis navikas. Nurodoma, kad klasikinė dermatofibrosarkomos forma labai retai metastazuoja, o fibrosarkominei jos transformacijai dažnai būdingos metastazės. Mes aprašome išopėjusios dešiniosios šlaunies dermatofibrosarkomos atvejį septyniolikos metų berniukui. Navikas buvo radikaliai pašalintas. Po vienerių metų atkryčio nerasta. Reikšminiai žodžiai: vaikų dermatofibrosarkoma, minkštųjų audinių sarkomos, fibrosarkominė transformacija, chirurginis gydymas


Introduction
Dermatofibrosarcoma protuberans (DFSP) was first described as a distinct clinicopathologic entity in 1924 (1), and it was approximately 30 years later when the tumor was first described in a child (2).Epidemiology shows 0.8-4.2cases per million persons per year and accounts for between 2% and 6% of all soft tissue sarcomas (3).It is an uncommon malignant neoplasm of the deep dermis and subcutaneous tissue, mostly affecting young and middle-aged adults (4).Men and women are equally affected (5).According to the WHO classification of the mesenchymal tumors, DFSP is an intermediategrade, locally-agressive tumor which recurs commonly but metastasizes very rarely (5).Because of a high local recurrence rate, the benchmark of the therapy is a wide surgical excision.On the other hand, complete resection carries the risk of a severe mutilation in relatively small children (6).
The alternative treatment options, such as chemotherapy or radiotherapy, have only minimal therapeutic effects (3).A novel targeted antitumor treatment is based on the specific molecular characterization of the DFSP.In over 90% of cases there is a 17q22; 22q13 translocation leading to a constitutive activation of the platelet-derived growth factor receptor (PDGFR) followed by a continuous stimulation of the tumor cells to grow (3,5,6).Initial studies with imatinib mesylate, a PDGF receptor-specific oral thyrosine kinase inhibitor, showed a response rate of 65% in patients with extensive local, recurrent or metastatic DFSP (5).

Case report
A 17-year-old boy had initially presented to a pediatric surgeon with a tumor on the proximal part of his right thigh.The mass measured 15 by 17 cm.It was irregular in form, fairly hard, and the overlying skin was tense and ulcerated.form can transform into fibrosarcomous DFSP (DFSP-FS), a more aggressive tumor with a higher metastatic potential (8) which may require a more intensive treatment approach.
In this age group, there are a number of soft tissue neoplasms which can have a similar appearance, location and growth type.The most common site of DFSP is the limbs (41%) and trunk (39%) (6).However, rhabdomyosarcoma is the most common soft tissue sarcoma in children (9) and may present on the limbs.Furthermore, rhabdomyosarcoma progresses quickly, and our patient complained that the mass grew in a year.About a quarter of primary leiomyosarcoma occur on the lower limbs, but usually they present in younger children.These tumors have very different treatment options.The decision to operate was based on the local growth of the tumor.
More than 90% of DFSP have a unique translocation involving chromosomes 17 and 22. Usually, CD34 is one of the most useful stains to differentiate DFSP from other soft tissue tumors.In approximately 3.2-15% of DFSP the tumor contains a high-grade fibrosarcomous component (3) which may present 20% to 80% of the tumor mass.These areas usually have a focal or diffuse loss of CD34 (10).A biopsy may hit the CD34-negative areas and give false negative results for dermatofibrosarcoma.In these cases, the RT-PCR analysis to determine translocation could be useful to diagnose dermatofibrosarcoma.
The primary treatment for DFSP is complete resection (3).The best method to remove these lesions is the Mohs micrographic surgery (1, 3) with a recurrence rate of 1.5% (2).In view of the infiltrative nature of DFSP, a wide excision (removal of 2-3 cm of uninvolved skin and the en bloc removal of the underlying subcutaneous tissue and fascia) had been widely accepted as the main treatment option (12).Furthermore, the average recurrence rate after a wide excision has been reported to be 8.8% (3).However, in our case, a wide surgical excision could cause considerable cosmetic and functional deformities.On the other hand, it has been reported that using conservative surgical margins the local recurrence rate may reach 39.7% (3).Our decision was to excise as widely as possible but leaving the least possible cosmetic and functional deformity.
Ultrasound revealed an irregular nonhomogeneous tumor with some signs of calcification.A color Doppler showed a good blood flow in the mass.CT clearly defined a homogeneous tumor in the dermis and subcutaneous tissue with a local contact to the right gracilis muscle (Figure 1).On post contrast CT, the tumor showed nonhomogeneous accumulation of contrast.
The potential malignancy of the tumor was predicted by its rapid growth, ulceration, and bleeding.The physical examination showed that the tumor was in the skin and subcutaneous tissue.CT revealed a limited, local growth of the tumor.It was decided to remove it surgically.
A spindle-shaped incision was made.The blood vessels were ligatured, and the mass was removed intact.Bone marrow biopsies were taken from both sides of the iliac wings to ascertain there were no metastases.
Histologically, the tumor was composed of a fibrous and myxoid tissue and variously cellular sheets of spindle-shaped cells with eosinophilic cytoplasm and uniform elongated nuclei.The tumor showed up to 5 mitoses per 10 HPF (Figure 2) and had areas with longitudinal fascicles of atypical spindle cells demonstrating more prominent nuclear atypia and mitotic activity: up to 10 mitoses per 10 HPF (fibrosarcomatous transformation).(Figure 3).The tumor cells were positive for CD34 and negative for heavy caldesmon, EMA, keratins, S100 protein, smooth muscle actin, desmin, myogenin, and MyoD1.(Figure 4).By RT-PCR analysis, the tumor exhibited t(17;22)(q22;g13) COL1A1/ PDGFB translocation.
The tumor reached the margin of the surgical excision.There were no metastases in the bone marrow biopsies.After reoperation, the histological examination showed no residual tumor.

Discussion
Dermatofibrosarcoma protuberans (DFSP) is a low -intermediate -grade cutaneous sarcoma which is rare in adults and even less common in children (7).Nevertheless, it is the most frequent skin sarcoma (3).DFSP shows a locally invasive and aggressive behavior and has a high recurrence rate but a limited metastatic potential (1% to 4%) (4,5).The metastatic potential depends on tumor type.Normally, DFSP is considered to be a tumor of low-grade malignancy.Rarely, this "classic" However, the postoperative positive surgical margins forced us to consider additional treatment options.Dermatofibrosarcoma protuberans is a radio-responsive tumor.The addition of postoperative radiotherapy reduces the risk of local recurrence in patients with narrow or positive surgical margins (13).Because of the high risk of gonadal dysfunction this treatment option was not suitable for our patient.
DFSP with fibrosarcomous transformation is resistant to conventional chemotherapy (3).A limited number of studies show that Imatinib mesylate can be effective in such cases (3,5,6).Unfortunately, our clinic is not able to offer this treatment because of its high costs.Reoperation was performed, and no residual tumor was found.After one year, there is no evidence of tumor recurrence.

Figure 1 .
Figure 1.Anterior contrast-enhanced CT scan shows a superficial soft tissue mass.Nonhomogenuous accumulation of contrast can be seen.It does not appear to invade the adjacent subcutaneous fat (white arrow)