Introduction

Dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue tumor originated from mesenchymal stem cells of reticular dermis. The incidence is around 0.8-4.5 cases/million/year. Young adults in the third to fifth decade are the most affected population, with a slight female predominance, in whom accelerated growth has been described during pregnancy [1]. The pathogenesis is unknown. It has been related to a chromosomal translocation t(17;22)(q22;q13), present in 90% cases of DFSP, that results in a fusion protein COL1A1-PDGFB (collagen type 1A1 geneplatelet -derived growth factor beta polypeptide gene) which leads to an overproduction of PDGF and cellular proliferation [2,3]. DFSP usually is presented as an indurated skin plaque, with slow growth. It involves dermis and subcutaneous fat, but rarely fascia and muscle. The most frequent location is trunk (50%), followed by extremities (35%). It presents a high risk of local recurrence (10-60%), but it is weird lymphatic dissemination and distant hematogenous metastasis (4-5%) (being lung the most frequent location) [4].

Histologically, it is characteristic a highly cellular diffuse dermal proliferation, with fusiform and hyperchromatic cells arranged in a storiform pattern (cellular swirls). Immunohistochemistry (IHC) is typically positive for CD34, vimentin, and negative for S-100. It has been described the fibrosarcomatous degeneration (7-16% of the cases), with more aggressive clinical behavior, and a higher local recurrence and distant metastasis rate. The higher rate of metastasis has been associated with factors such as the level of invasion (depth), ulceration, necrosis, affected borders and tumor differentiation degree [5,6]. The highest risk of local recurrence is in the first 3 years, so it requires a close clinical follow- up, and thoracic CT scan in case of aggressive variants [7,8].

The treatment of DFSP is surgical removal with wide local excision, although Mohs micrographic surgery (intraoperative histopathologic margin control) achieves a decisive role in regions where tissue preservation is a priority. Its prognosis is good, with a 10- year overall survival of 99% of patients [7,8]. Imatinib mesylate, a tyrosine kinase inhibitor, has been recently approved for recurrent, unresectable, or metastatic DFSP in patients with the PDGFB mutation previously described [8].

We present a case of a 40-year-old woman with no medical backgrounds (just 3 pregnancies and 3 vaginal deliveries), who consulted for the first time in 2008, in a peripheral hospital, for an infraumbilical cutaneous nodule, during first pregnancy. It was surgically removed and the histopathological exam showed a fibrocystic lesion. After that, she presented two recurrences (also while pregnancies) in 2014 and 2015, that were removed and with a histopathological exam of nodular fasciitis. In September 2018, a new indurated plaque appeared with a faster growth in the same location, and she was refered to our Sarcoma Unit.

She presented a subcutaneous infraumbilical mass of 5x4cm in diameter (Figure 1), well- defined borders, fixed to the skin but not to deep layer. An expert sarcoma pathologist analyzed the previous histopathological samples. Because a DFSP was suspected on microscopy, histochemistry was performed, being positive for CD34, ML actin, vimentin and bcl2, and negative for F.XIIIa, S-100. Molecular cytogenetics study was also carried out by fluorescence in situ hybridization (FISH), showing a positive rearrangement for the PDGFB gene. Surgical removal with wide local excision was performed. An infraumbilical tumor of 5.2 x4 cm was found in dermis and subcutaneous cellular tissue, reaching the fascia without invading it. Block exeresis was performed, including skin, subcutaneous and fascia with margins of 3cm in all directions. Fragments from 4 cardinal points were analyzed intraoperative, reported tumor free. Anterior abdominal fascia was closed with a Marlex mesh and primary skin closure was possible.

The histological analysis showed a mesenchymal proliferation with a storiform pattern in the shallow region according to a DFSP, and a fishbone pattern with fusiform cells corresponding to a fibrosarcoma in the deeper region. IHC: CD34 +, actin HHF35 +, XIII factor + (Figure 2). The final diagnosis was a FIBROSARCOMA GRADE 2 of the FNCLCC pT2N0M0, with respected margins. The deep fascial margin was negative, although it was close to the tumor (2mm). As it was a surgical barrier (fascia), margin extension was not considered necessary. The Sarcomas Multidisciplinary Team recommended close follow-up with local exploration and thoracoabdominal-pelvic CT scan. No distant lesions were found. A proper identification of this type of tumor, with an early and precise diagnosis, is very important. It may change the surgical procedure and the disease prognosis. For all these reasons we strongly suggest that skin lesions with nonclear pathologic diagnosis or recurrent lesions) to be managed by expert pathologists and a Multidisciplinary Team on soft tissue sarcomas in order to achieve the best results.

Compliance with Ethical Standards Conflicts of Interest

No conflicts of interest to declare in this study.

Research Involving Human Participants and/or Animals

This is a descriptive case report study. No other researching involving humans or animals have been developed. Information related to participant will be kept confidential and managed in accordance with Data Protection Law.

Informed Consent

The informed consent to participate in this descriptive case report study was signed by the patient.

Acknowledgement

Acknowledgement to “Peritoneal and Retroperitoneal Unit”, Plastic Surgery and Histopathologists team from Hospital General Universitario Gregorio Marañón.

References

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4. NCCN Guidelines Version 1.2019. Dermatofibrosarcoma protuberans
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