Transformation of Dermatofibrosarcoma Protuberans into a Fibrosarcoma.

Dermatofibrosarcoma protuberans is a rare cutaneous mesenchymal tumor characterized by a low potential of malignancy with a very low rate of metastasis but an important rate of local recurrence. Its transformation into a fibrosarcoma is exceptional, responsible for a higher metastatic potential. This transformation implies a closer surveillance. Through a case report and literature review, we will try to expose epidemiological, clinical, histological, therapeutic, and outcome particularities of this entity.

What was known?

Dermatofibrosarcoma protuberans is a relatively rare skin tumor characterized by a low potential of malignancy.

Introduction

Dermatofibrosarcoma of Darier-Ferrand or dermatofibrosarcoma protuberans (DFSP) is a rare cutaneous mesenchymal tumor characterized by a low potential of malignancy with a very low rate of metastasis but a rate of local recurrences rather important. The transformation of a DFSP into a fibrosarcoma (FS) is exceptional. This transformation is responsible for a significant metastatic potential.[1] Through clinical observation, the authors report the epidemiologic, clinical, histological, therapeutic, and evolutionary characteristics of the disease.

Case Report

We report the case of a 19-year-old female, without any pathological history, presenting a cutaneous mass of the lower third of the right upper leg that appeared 7 years ago. The clinical study showed an 8 cm diameter mass located on the anterior and internal side of the distal third of the right upper leg. This mass was firm, painless, vascularized, nodular, and polylobulated. It was dependent on the superficial cutaneous tissues and evoking a tumor of Darier and Ferrand [Figure 1]. No weight loss was noted. No systemic adenopathy or signs of distant metastasis were found on the chest, abdomen, and pelvis computed tomography scan. A magnetic resonance imaging study of the right lower extremity revealed an 8 cm × 8 cm × 5.7 cm well limited, vascularized, round mass in the cutaneous, and subcutaneous tissues [Figure 2]. The patient underwent a 5 cm margin excision involving in-depth the aponeurosis with resection margins microscopically negative [Figure 3]. The residual skin defect was grafted. The histological study revealed a malignant transformation of the dermatofibrosarcoma of Darier and Ferrand into a sarcoma [Figures 4 and 5]. The esthetic and functional result was assessed as good. There was no recurrence at 5 years follow-up [Figures 6 and 7].

Figure 1

Clinical aspect of the mass evoking a tumor of Darier and Ferrand

Figure 2

Magnetic resonance imaging noted a well limited, vascularized, round mass of cutaneous and subcutaneous tissues

Figure 3

Resection of the tumor with a margin of excision of 5 cm involving in-depth the aponeurosis. The residual skin defect was grafted

Figure 4

Histological aspect revealing a malignant transformation of the dermatofibrosarcoma of Darier–Ferrand into a sarcoma (H and E stain, ×100)

Figure 5

Tumoral proliferation in spindle-shaped cells (H and E stain, ×400)

Figure 6

The esthetic and functional result was assessed as good at 5 year follow-up

Figure 7

The esthetic and functional result was assessed as good at 5 year follow-up

Discussion

Cutaneous sarcomas represent <1% of all cancers. The DFSP generally occurs in the young adult between 20 and 40 years. There is a discrete male prevalence. The transformation of a dermatofibrosarcoma of Darier and Ferrand into an FS (FS-DFSP) is exceptional, until now and since the first description of a metastatic DFSP by Penner[2] in 1953, only 100 cases of FS-DFSP were reported. The DFSP generally occurs in the trunk (47%), the upper limb (38%), or the cervico-cephalic area (15%). This tumor generally begins with a single swelling, hardened by place, brown-red, purplish. After several years (a few decades), one or more nodules become rising protuberant. After a long time superficial growth, this tumor will invade the deeper layers extending along the fascia. No significant clinical difference was noted between FS-DFSP and the traditional form. The tumoral proliferation of the DFSP interests cutaneous and sub cutaneous layers of the skin; it is made up of spindle-shaped cells with few atypies and mitosis. In the periphery, the tumoral cells are arranged in great corrugated and flexuous beams loose parallelism at the surface. In depth, the tumor infiltrates the sub-dermal in tablecloth dissociating the fat lobules and takes the form of interlobular partitions. It can extend from the primary zone, reaching the underlying fascia or aponeurotic layer.

The tumoral cells of the DFSP express the CD34 in 90% of the cases and factor XIII. The PS100 does not express.[3] The FS-DFSP is defined histologically by the presence in a cellular DFSP of ranges pointing towards an FS, the transition is abrupt or gradual. Cell areas are characterized by a chevron fascicular architecture and high mitotic activity.

The treatment of these cutaneous tumors, mainly surgical, is based on broad resection in the case of malignant tumor. The safety margins vary from one tumor to another.[45] Adjuvant radiotherapy can be used to obtain local control when the resection margins are microscopically positive or when wide excision results in a significant functional or esthetic deficiency.[6] The evolution of the DFSP is slow, and frequently recurrences occur. Their frequencies depend on the margins of the initial excision: 40% if they are 2 cm, 10–20% for margins of 3 cm, and 1.75% for margins of 4 cm. In all the cases, the excision must carry in depth a safe aponeurotic layer. Metastasis are rare (5%) mostly pulmonary.[3] The relationship between the presence of fibrosarcomatous foci with locoregional or metastatic evolution remains controversial.[78] The rate of locoregional recurrence of the FS-DFSP depends on the quality of the resection, without a significant difference compared to DFSP. On the other hand, the free interval, preceding the possible recurrence, could be shortened (usually <2 years) compared to the traditional form.[9] A large study published by Mentzel et al.[10] showed an association between the presence of fibrosarcomatous foci and significant metastatic potential. In this study, approximately 15% of the patients developed primarily pulmonary metastases without significant association with the prognostic factors such as the size of the lesions, the mitotic activity or the presence of necrosis.

Conclusion

The DFSP is a rare tumor, its diagnosis is histological, and its treatment is surgical. The transformation of a DFSP into an FS is exceptional. This transformation seems to be in association with a significant metastatic potential estimated at 15%. The identification of fibrosarcomatosis implies a complete assessment of extension and a closer follow-up.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

What is new?

The transformation of DFSP into a FS is exceptional and comes with a high potential of malignancy. However, a broad resection with safety margins could lead to a cure.