Uncommon presentation of dermatofibrosarcoma protuberans: extensive growth in a rare location with subclinical cutaneous manifestation—a case report

Abstract

Dermatofibrosarcoma protuberans (DFSP) is a rare, locally aggressive cutaneous tumor predominantly affecting young to middle-aged adults, characterized by a slow-growing, indurated plaque or nodule. The diagnosis and treatment of DFSP can be challenging due to its rarity, growth pattern and variable clinical presentation. A 40-year-old male presented with a firm lump of 8 mm on his forehead for one year. It was initially suspected to be a benign lipoma or atheroma and removed accordingly by a private plastic surgeon. However, histopathological examination revealed dermatofibrosarcoma protuberans (DFSP) that was not radically removed, prompting referral for removal at our department. Here, he presented with a scar of 10 mm with no visible or palpable residual tumor. A planned excision of 20 mm and reconstruction with split thickness skin graft (STSG) was performed. Histopathology showed tumor activity at several margins, with perineural and periosteal invasion. MRI was inconclusive, and therefore PET-CT was added, which showed possible residual tumor. Re-excision including mapping biopsies was performed. Wide re-excision was performed three times to achieve clear surgical margins, yielding a tumor size of approximately 8x10 cm and a final defect measuring 10x12 cm. The defect was reconstructed with a dermal template (Integra^®) and STSG. Our case underscores the propensity of DFSP for significant subclinical extension, including potential perineural and periosteal invasion. Despite the aesthetically challenging location, a satisfactory cosmetic result was achieved, and there was no recurrence during the two-year follow-up.

Introduction

Dermatofibrosarcoma protuberans (DFSP) is a rare, locally aggressive cutaneous tumor of intermediate to low-grade malignancy [1].

This soft tissue sarcoma typically presents in the dermis and subcutaneous tissue, with a predilection for the trunk (approximately 50% of cases) and proximal extremities (∼30%), while the head and neck region is less commonly involved (∼10–15%) [2]. DFSP typically manifests as a slow-growing, indurated plaque or nodule, often with a reddish or violaceous hue [3]. The tumor often develops insidiously over months or years and may gradually enlarge and become protuberant. The lesion is usually painless [3,4].

Tumor size range from 0.5 to >10 cm in diameter, with a mean of 2–3.5 cm [4]. While DFSP can occur at any age, it predominantly affects young to middle-aged adults, with a peak incidence in the third to fourth decades of life [1]. The diagnosis of DFSP poses challenges due to its rarity and variable clinical presentation. Sometimes DFSP can mimic benign conditions such as dermatofibroma, morphea, or even lipomas. In rare cases, an atrophic variant can present as a depressed, skin-colored lesion, leading to misdiagnosis [3]. Histologically, DFSP is characterized by bland spindle-cells arranged in a storiform pattern with extension into the deep dermis and subcutaneous fat, often in a honeycombing pattern. The tumor typically shows diffuse positivity for CD34 [4,5].

Management of DFSP involves complete surgical excision with wide margins to reduce the risk of local recurrence, which is a hallmark of this tumor [6]. Achieving clear margins can be challenging, especially in anatomically complex locations or cases with extensive involvement [7]. Follow-up of DFSP patients is crucial to monitor for local recurrence, which can occur years after the initial treatment [8].

Imaging modalities such as PET-CT and MRI play a role in assessing treatment response and detecting potential metastasis, although DFSP has a low metastatic potential [9]. Long-term follow-up is essential to ensure early detection of recurrence and optimize patient outcomes [10,11].

In this case report, we present a rare case of DFSP with subclinical aggressive spread in a cosmetically and functionally sensitive area. We aim to contribute to the understanding of DFSP’s atypical presentations and emphasize the importance of thorough histopathological assessment and multidisciplinary management.

Description of the case

The case report discusses a 40-year-old male with well-controlled hypertension on enalapril, who presented with a firm lump of 8 mm on his forehead. It was initially suspected to be a benign lipoma or atheroma and was therefore excised by a private plastic surgeon.

Histopathological examination revealed dermatofibrosarcoma protuberans (DFSP) not radically removed, and the patient was referred for removal at our department. Here, he presented with a scar of 10 mm with no visible or palpable residual tumor. The scar was re-excised to 20 mm to the periosteal plane, and the defect was covered with a split-thickness skin graft (STSG) while awaiting histopathological assessment.

Histopathology revealed tumor activity at several margins, including perineural and periosteal invasion and immunohistochemistry was positive for CD34.

There were no signs of fibrosarcomatous differentiation. Mohs micrographic surgery was not performed as it is not a common clinical practice in our department. Standard wide local excision with intraoperative margin assessment was chosen to ensure clearance prior to reconstruction.

MRI was performed and revealed possible tumor activity at the margins but was inconclusive. See Figure 1. The patient was then discussed at the multidisciplinary tumor board, consisting of tumor onco­logists, radiologists, a pathologist and a plastic surgeon. A further re-excision of 5–10 mm was recommended, including mapping biopsies.

Figure 1.

MRI imaging prior to second re-excision showing possible tumor activity at the margins.

During re-excision, perioperatively suspicious tumor material was seen at the left border. A biopsy was taken and sent to the pathologist for immediate assessment. As it turned out to be residual DFSP, a total excision of 3 cm was excised at the left border of the defect. The periosteum was resected in all areas of potential involvement.

Mapping biopsies were performed to evaluate further growth. A total of 12 mapping biopsies at a distance of 1 and 2 cm from the defect were taken using a 2 mm punch biopsy.

Histopathological evaluation after two weeks confirmed that all mapping biopsies were negative; however, tumor activity was still present at the left border from 12 to 6 o’clock.

This resulted in an additional excision of 20 mm on the left side to obtain clear margins. In total, wide excision was required three times to achieve clear margins and complete excision.

This resulted in a final defect measuring 10 × 12 cm and a tumor size of approximately 8 × 10 cm.

The defect was reconstructed with a dermal template (Integra^®) and STSG in a two-stage procedure. See Figure 2.

Figure 2.

A: Patient at initial contact; B: patient after final revision surgery; C: patient 12 months after final revision surgery. D: patient 30 months after final revision surgery.

In terms of follow-up, the patient’s care plan included regular monitoring for relapse through clinical controls every 3 months and MRI scan every 6 months for the first two years. Baseline PET-CT imaging was performed and showed no dissemination. The patient’s current status of being followed up for 30 months shows no relapse. We plan on following the patient for a total of five years.

Discussion

This case report documents an uncommon presentation of dermatofibrosarcoma protuberans (DFSP) in a cosmetically and functionally sensitive area, the forehead, demonstrating extensive subclinical spread, including perineural and periosteal invasion, despite an initially subtle clinical appearance. Although DFSP is recognized for its tendency toward subclinical extension, few reports have described such aggressive infiltration in the absence of overt surface changes.

Moreover, the substantial size of the lesion and its aggressive growth pattern into the periosteum and nerves without any macroscopically visible appearance further complicated management of this tumor. While DFSP is known for its local aggressiveness, infiltration into deeper structures such as periosteum and nerves are less common [8]. The aggressive behavior of the tumor in this case necessitated multiple re-excisions including the removal of the periosteum resulting in a much more advanced reconstruction. The utilization of a dermal template (Integra^®) in conjunction with split-thickness skin graft (STSG) facilitated effective wound closure and functional restoration.

The inconclusive findings on MRI serve as a reminder of the limitations of diagnostic imaging modalities in accurately characterizing DFSP. Despite its utility in delineating tumor extent and guiding surgical planning, MRI may fail to detect microscopic tumor infiltration or subtle anatomical involvement, as evidenced in this case. This underscores the complementary role of clinical and histopathological evaluation in confirming diagnosis and guiding therapeutic interventions, particularly in cases with atypical clinical and radiographic features [12].

Methods of complete circumferential and deep margin assessment, such as Mohs micrographic surgery (MMS), have demonstrated reduced recurrence rates in DFSP and are particularly advantageous in anatomically sensitive areas or recurrent disease. Recent studies have shown that MMS can achieve recurrence rates as low as 0.4% over a five-year follow-up period [13]. However, despite these benefits, MMS presents limitations in cases of large tumor burden. In this particular case, the size and extent of the tumor made MMS technically challenging and logistically impractical. Additionally, MMS is not the standard of care for DFSP in Denmark, where surgical management typically relies on intraoperative collaboration with pathologists. During surgery, representative tissue samples are sent for immediate pathological evaluation, leveraging the specialized expertise of pathologists over that of the surgeon in margin evaluation [14].

Nevertheless, due to the tumor’s considerable size, it was not feasible to assess all margins in real-time. As a result, a wide local excision (WLE) was performed. WLE is a widely accepted and established treatment modality for DFSP, offering good oncological outcomes when combined with appropriate margin planning. One of the key advantages of WLE is its applicability to large lesions and its relative simplicity compared to MMS. However, WLE is associated with a higher risk of local recurrence when margins are insufficient, with recurrence rates reported up to 13% [15]. Furthermore, WLE can result in significant tissue loss and may pose reconstructive challenges, particularly in functionally or cosmetically sensitive areas.

In this case, WLE in combination with perioperative mapping, was considered the most practical and effective approach, balancing oncologic control with available resources and national treatment guidelines.

The patient follow-up included regular monitoring for relapse through clinical controls every 3 months and MRI scan every 6 months for the first two years. The patient also had PET-CT at baseline. At 30 months follow-up no relapse had occurred.

Although not utilized in the present case, adjuvant radiotherapy may be considered in selected complex cases as part of a conservative local treatment approach, particularly when complete surgical excision is challenging or infeasible [16].

Conclusion

In conclusion, this case illustrates the diagnostic and therapeutic challenges posed by atypically located DFSP with extensive subclinical spread. Despite the lack of visible tumor, histopathology revealed perineural and periosteal invasion, highlighting the importance of wide surgical margins. The case also demonstrates that satisfactory cosmetic and functional outcomes can be achieved using advanced reconstructive methods, such as dermal substitutes and skin grafting. Long-term multidisciplinary follow-up remains essential due to the risk of local recurrence and the potential for secondary malignancies.

• The authors have no competing interests to declare

• We hereby confirm that informed written patient consent has been obtained. We have also obtained written patient consent to use the provided images. Documentation can be provided if wanted.

• All pictures should be in color

• Declarations of interest: none

Contributors

Author/Corresponding Author: Zain Elabedin Asheer, E-mail: Zainasheer1994@gmail.com. Address: Department of Plastic Surgery and Burns Treatment, Rigshospitalet, Blegdamsvej 9, 2100 København Ø, Copenhagen University Hospital, Denmark.

Supervisor/Senior Author: Jennifer Berg Drejøe. Address: Department of Plastic Surgery and Burns Treatment, Rigshospitalet, Blegdamsvej 9, 2100 København Ø, Copenhagen University Hospital, Denmark.

Disclosure statement

No potential conflict of interest was reported by the author(s).