Management of two rare cases of dermatofibrosarcoma protuberans arising in the parotid region

Abstract

Dermatofibrosarcoma protuberans (DFSP) is a rare cutaneous tumour, accounting for less than 1% of malignant tumours of the head and neck region. This tumour rarely presents metastatic disease, but has a high recurrence rate. Therefore, wide surgical excision with microscopically free margins is the therapeutic gold standard. Only five cases are described in literature of this tumour arising in the parotid region, a site that presents challenges both in achieving a wide demolition and in reconstructing the resulting defect. Here we describe two cases of DFSP arising in the parotid region that were treated surgically, achieving microscopically free margins. Reconstruction of the vast skin defect was achieved by means of a supraclavicular artery island flap, with good functional and aesthetic results.

Background

As first described by Darier and Ferrand in 1924, dermatofibrosarcoma protuberans (DFSP) is a rare cutaneous fibrohistiocytic neoplasm.¹ It is considered a neoplasm of intermediate malignancy as it is a slow-growing, locally highly invasive and easily recurring tumour, but with a low risk of distant metastases.² It accounts for about 1% of soft tissues sarcomas and has an incidence of about 0.8–5 cases per million population.¹ DFSP occurs most frequently on the trunk (42%), followed by upper extremities, lower extremities and head and neck (16%).³ It has a very unspecific clinical appearance, often presenting as a slowly progressive cutaneous lesion, which makes it very common for the diagnosis to be delayed, as oftentimes these lesions are mistaken for benign skin conditions.^{4 5} The therapeutic gold standard is complete surgical resection, with microscopically clear margins: some authors recommend more than 2 cm of grossly uninvolved margin of skin and underlying deep fascia.⁶ Radiotherapy may also play a role, as adjuvant therapy or in those cases in which surgical excision is not feasible.²

DFSP of the head and neck accounts for less than 1% of malignant tumours of the district and about 7% of head and neck sarcomas.⁶ DFSP of the head and neck has been reported to have a higher recurrence rate than in other locations⁷: this may be due to the fact that achieving clear margins of 2 cm or more in the head and neck region is much more difficult than in other districts, because of its complex anatomy and function. Also, large resections in the head and neck region are most times not amenable for primary closure and make it necessary to harvest pedicled or free flaps in order to reconstruct the defect.

We hereby present two cases of DFSP of the skin of the parotid region that were treated surgically with a wide resection, with consequent reconstruction of the defect by means of a supraclavicular artery island flap (SCAIF).

Case presentation

Case 1

A 30-year-old woman with no significant medical history, presenting with an extensive lesion of the skin of the right parotid region. When she came to our attention, the lesion had been present for about a year and a biopsy carried out in another centre suggested the presence of DFSP. The lesion presented as an erythematous plaque of about 6 cm in greatest dimension, of hard consistency and multilobulated (figure 1). A contrast-enhanced MRI confirmed an alteration of signal of skin and subcutaneous tissue, in correspondence of the entire length of the right parotid gland. A total body positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (18-FDG) showed no significant abnormalities in the distribution of the radioactive tracer.

Figure 1.

DFSP of the right parotid region presenting as an erythematous plaque of about 6 cm in greatest dimension. DFSP, dermatofibrosarcoma protuberans.

We decided to treat the condition surgically, by excising it together with the entire right parotid gland (right total parotidectomy); a right selective nodal dissection was also performed (levels IIa–IIb–III). Reconstruction of the minus of skin in the preauricular area was achieved by means of a right SCAIF.

In order to achieve a better aesthetic result, we decided not to deepithelise and tunnel the proximal portion of the flap, but to leave it exposed, always covered with a non-adhering dressing in order to keep it moist (figure 2). Histological examination confirmed the presence of a DFSP extended to the parotid gland, with clear margins and no nodal extension (figure 3).

Figure 2.

Immediate postoperative appearance of the patient. Flap pedicle exposed.

Figure 3.

Dermatofibrosarcoma protuberans (H&E).

The patient was discharged from our clinic 5 days after surgery with no complication and no deficit of the right facial nerve. Four weeks after the first surgery, the supraclavicular flap was autonomised under general anaesthesia, with no complication (figures 4–6).

Figure 4.

Intraoperative picture: flap ischemisation.

Figure 5.

Immediate postoperative appearance of the autonomised flap.

Figure 6.

Appearance of the patient 10 days after flap autonomisation.

Case 2

A 53-year-old man with a previous diagnosis of a DFSP of the left pretragal skin. The patient had already undergone surgery once to remove the lesion (in 2018), and once again after its recurrence. After the second excision, the histological examination showed a persistence of disease on the margins of resection, which made it necessary for a radicalisation.

When he came to our attention, the patient was left with a vast minus of skin in the left pretregal area, where the tissues were left for secondary healing, and a deficit of the temporal branch of the left facial nerve (figure 7).

Figure 7.

Minus of skin in the left pretragal area after previous excision of DFSP. DFSP, dermatofibrosarcoma protuberans.

We performed a left total parotidectomy, extended to the overhead skin and soft tissues and a left nodal dissection (levels IIa–IIb–III). A left SCAIF was used to reconstruct the defect. As we did for the patient in case 1, we decided not to deepithelise and tunnel the proximal portion of the flap, but to leave it exposed and successively autonomise it (figure 8). Histological examination confirmed the presence of DFSP extended to the periparotid fat tissue, with no nodal extension (figure 9).

Figure 8.

Immediate postoperative appearance of the patient. Flap pedicle exposed.

Figure 9.

Dermatofibrosarcoma protuberans (H&E).

The patient was discharged 5 days after surgery, with no complication.

Four weeks later, the flap was autonomised under general anaesthesia (figures 10 and 11); the patient was discharged the following day without complications (figure 12).

Figure 10.

Intraoperative picture: flap ischemisation.

Figure 11.

Immediate postoperative appearance of the autonomised flap.

Figure 12.

Appearance of the patient 10 days after flap autonomisation.

Outcome and follow-up

The patients are at the moment 2 and 4 months postoperative and disease-free. They will be kept under close follow-up by means of contrast-enhanced MRI and clinical evaluation every 2–3 months.

Discussion

DFSP of the head and neck is a rare clinical entity, accounting for less than 1% of malignant tumours of the region. Being a locally invasive tumour with a propensity for subclinical involvement, local recurrence is dreaded but not uncommon⁸; this is mostly due to the fact that DFSP usually grows asymmetrically, often with finger-like projections, which translates to an analogous microscopic structure.¹ Furthermore, this tumour is often misdiagnosed as a benign condition, given its slow-growing rate, and for this reason it may be treated inadequately at first,⁹ surgical excision with wide microscopically free margins being the therapeutic gold standard.⁸ However, DFSP rarely metastasises, with less than 5% of patients developing metastatic lesions, which represent a poor prognostic sign.¹ Thus, overall 5-year survival rates for DFSP have been reported to be as high as 99%.²

A brief literature search reported only about 200 publications on DFSP of the head and neck region, with only five describing cases of the tumour arising in the parotid region.^10–14 In all cases of DFSP of the parotid region found in literature, the tumour had recurred at least once after surgical excision, also due to the fact that some of these tumours were at first mistaken for primitive salivary tumours and not treated adequately. This underlines the importance of a wide surgical excision, with wide microscopically free margins, in order to reduce the chances of local recurrence. However, given its conformation and the density of vital structures present in the head and neck region, obtaining wide resections is not as agile as it is in other body sites. Hence, DFSP of the head and neck is reported to have a higher recurrence rate and a worse prognosis than in other body regions.^{10 15} Furthermore, after major demolitive surgery of the head and neck region, reconstruction is often needed as primary closure is often not feasible. This represents a challenge both under the functional and the aesthetical point of view.

In the two cases presented herein, the lesion had been present for at least a year, slowly growing in size. In both cases, the tumour had started to invade the neighbouring tissues, in particular, the parotid gland and the periparotid fat tissue; thus, in order to achieve a complete excision with microscopically clear margins, it was necessary to excise the parotid gland together with the overlying skin. In both cases, the resection was very extensive, due to the considerable size of the lesion; it was thus necessary to harvest a flap in order to reconstruct the vast defect. Nowadays, microvascular-free flaps are considered to be the gold standard in head and neck reconstruction after major surgery, as they are extremely versatile and have a very high success rate.¹⁶ Sometimes, however, pedicled regional flaps represent a better reconstructive option and an easier surgical procedure, particularly in elderly or comorbid patients.¹⁷ In particular, in our experience, the SCAIF represents a very good alternative, especially when reconstructing skin defects of the head and neck region. The SCAIF is an easy and quick-to-harvest flap living on a perforator of the supraclavicular artery (figures 13 and 14), a branch of the transverse cervical artery. It is a very pliable and not bulky flap, especially when compared with other pedicled flaps such as the pectoralis major flap.¹⁸ This flap is most commonly used in reconstruction after demolitive surgery for head and neck cancer, especially in those patients with comorbidities or of more advanced age, for whom the prolonged operative time required by the use of a microvascular free flap is not advisable. The position of this flap allows for a good arc of rotation, sufficient for the reconstruction of most head and neck subsites. When reconstructing a portion of the upper aerodigestive tract, the proximal portion of the flap is usually deepithelised and tunnelled, while this is not usually necessary when the flap is used to reconstruct a skin defect.^{18 19} In our experience, the SCAIF is an extremely reliable and safe flap, with reproducible results.^{19 20}

Figure 13.

Surgical technique: the vascular pedicle is in a triangular region (green dotted line) between the sternocleidomastoid muscle (SCM), the external jugular vein (EJV) and the clavicle (clav). The flap (blue dotted line) lives on a perforator of the supraclavicular artery (red).

Figure 14.

Surgical technique: harvesting and insetting of the flap.

Another flap commonly used in the parotid region is the anchor tragal flap, which is used after ritidectomy, in order to achieve a better aesthetic result.²¹

In the two cases hereby presented, the decision to use a SCAIF as a reconstructive method was made especially keeping in mind the aesthetic result we wanted to achieve, as the colour of the skin of the supraclavicular region most closely resembles that of the skin of the parotid region. Furthermore, in order to obtain an even better aesthetic result, we decided not to deepithelise and tunnel the more proximal portion of the flap, but to leave it exposed and successively surgically autonomise the flap. The pedicle of the flap was thus left exposed for about 4 weeks, covered with a non-adhering dressing in order to keep it moist. After autonomisation, the patients were left with a good aesthetical result, with skin matching in colour that of the remaining head and neck skin, and without the bulk that a tunnelled pedicle would leave in the supraclavicular region. Also, in our experience, leaving the pedicle exposed does not increase the risk of infection, as neither patient incurred in any local or systemic complication.

Learning points.

• Dermatofibrosarcoma protuberans (DFSP) is a rare tumour, unlikely to metastasise and with an overall good prognosis, but with a high local recurrence rate. DFSP of the head and neck region has worse prognosis and higher recurrence rates compared with other body sites.

• Wide surgical excision with wide microscopically free margins is the therapeutic gold standard and the best weapon in order to reduce the chances of local recurrence.

• Only five cases of DFSP of the parotid region are described in literature: the parotid region represents a challenge both in achieving a wide resection and a functionally and aesthetically satisfying reconstruction.

• The supraclavicular artery island flap is an excellent choice for reconstructing defects of the head and neck region, with good texture and colour match.

Ethics statements

Patient consent for publication

Obtained.