A novel method of assessing intraoperative surgical margins in patients with dermatofibrosarcoma protuberans: A specimen radiography system

Introduction

Dermatofibrosarcoma protuberans (DFSP) is a rare mesenchymal tumour of intermediate-grade malignancy. The tumour is characterised by slow infiltrative growth and a high rate of local recurrence.¹ Effective surgical treatment features wide local excision (WLE) with surgical margins of 1 to 2 cm and requires negative pathological margins.² Even after optimal preoperative evaluation, it can be difficult to determine the surgical margins required to achieve pathological negativity. The National Comprehensive Cancer Network (NCCN) and European multidisciplinary experts recommend a margin of 2–4 cm, thus up to the deep fascia or pericranium and, if clinically feasible, with confirmed pathological negativity.³ In practice, however, it is almost inevitable that such incisions will be associated with serious facial and/or functional defects, particularly in areas where the anatomy is challenging, such as the head and neck.⁴

Given the propensity of DFSP to recur, Mohs micrographic surgery (MMS), a technique that ensures complete margin assessment with tissue preservation, has been suggested as a treatment for DFSP.^4,5 However, it is a very elaborate approach, requiring a great deal of training and a special ancillary team which limits its applications. It is also very labour-intensive, requiring the preparation and review of multiple histological tumour sections while the patient waits. For many patients, a phased surgical procedure (‘a slow Mohs’) is done which requires many hours.⁵ MMS is both costly and inconvenient.^6,7 An ideal method should save cost and be rapid. Recently, new imaging techniques such as ex vivo confocal microscopy are developing as a fast alternative to MMS.⁸ Here, we introduce an intraoperative specimen radiography system that enhances the surgical management of DFSP. Although specimen radiography is established for breast tissue imaging, its use for intraoperative DFSP margin analysis is novel in the field of oncoplastic surgery.

Patients and Methods

Screening of surgical specimens

We used the Trident intraoperative specimen radiography system (Hologic, Marlborough, MA, USA) [Figure 1]. The lighted specimen X-ray chamber is covered by lead, thus the device can be placed in the operating room without additional radiation protection.

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Figure 1:

View of the specimen radiography system (HOLOGIC, Marlborough, MA, USA). This mobile digital specimen radiography unit is composed of a display device, computer and screening box. The system can be easily moved into the operation room.

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Immediately after excision, the specimen was placed in a specimen bag [Figure 2] and imaged at 1× magnification with automatic exposure control. The entire specimen was screened. Multiple images were acquired if needed, although no specific operational guidelines on orientation or the number of projections were mandated. More details about this device can be seen on the website: https://www.hologic.com/hologic-products/breast-health-solutions/trident-specimen-radiography-system

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Figure 2:

Immediately after surgical excision, the specimen was conceptualised into a plastic bag. This plastic bag prevents specimens from contaminating the screen box without affecting image quality.

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Results

Margin analyses

The mean duration of specimen radiography was 9.7 ± 2.3 min (range 7–13 min). Intraoperatively, negative margins were radiographically observed [Figure 3]. The minimal radiologic lateral margin width [Figure 4] ranged from 5.0 to 35.4 mm (mean 16.9 ± 10.4 mm). The negative margins were postoperatively confirmed. The minimal pathologic lateral margin width ranged from 4.0 to 34.5 mm (mean 16.6 ± 10.1 mm). No positive margins were found both with radiography and pathology.

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Figure 3:

The entire specimen of waist from a man was imaged with the system in magnification 1.0x with exposure mode of ‘AutoKy’.

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Figure 4:

The width of lateral margin can be gauged by scale in the specimen of waist from a man by the radiography system. The minimal lateral width can be observed and scaled.

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Discussion

DFSP is a rare, superficial soft tissue sarcoma. Its rarity precludes large prospective studies and thus the optimal specimen margin for the attainment of local control remains unclear. Extensive, abnormal local invasion is associated with a high recurrence rate.⁹ Resection margin width is strongly correlated with local DFSP control; recurrence rates are higher when margins are ‘conservative’.^10,11 Surgical excision with meticulous evaluation of all margins is the mainstay of DFSP treatment and is essential to ensure a long-time cure and low morbidity.

Generally, complete DFSP surgical resection is accomplished via either MMS or a standard WLE. The choice should be dictated by the need to completely excise the carcinoma with negative margins (tantamount to a cure); to preserve function, optimise cosmesis, minimise morbidity; and to minimize cost and inconvenience to the patient and the healthcare system. Both WLE and MMS allow attainment of the first goal, but attainment of the second and third goals is more difficult.^12,13 These goals pose major challenges to oncoplastic surgeons; we were thus encouraged to test a novel method and explore a new field.

Specimen radiographic devices allow rapid and effective intraoperative assessment of excised tissue. Faxitron was the first to introduce such a device in 1998. Since that time, several other systems have become available, including BioVision (Faxitron Bioptics LLC, IL, USA) and Trident. There is no need to transport specimens from the operating room to the pathology department, thereby streamlining the workflow.¹⁴ To the best of our knowledge, this is the first application of a specimen radiographic system for intraoperative margin assessments of DFSPs.

System operation is simple and brief. The differences between margins identified via intraoperative radiography and pathology was non-significant. Specimen radiography sensitively assesses surgical margins intraoperatively.

There were some limitations to our study. It was not randomised and because the sample size was small, we could not calculate positive or negative predictive values. A multi-institutional study with a larger number of patients is required. We believe that several radiologists should collaborate in a future study.

Conclusion

Intraoperative specimen radiography systems were introduced in the 1990s and are commonly employed during breast surgeries. However, no report has yet described the use of such a system during oncoplastic surgery. Here, we present our system and explore its utility.

Our method of intraoperative margin assessment during DFSP surgery is promising as the operative time is much shorter than that of the Mohs procedure. We believe that specimen radiography can be used to assess margins in patients with cutaneous soft tissue cancers such as DFSPs, basal cell carcinomas and squamous cell carcinomas. As the method expands into new areas within oncoplastic surgery, more reports with longer follow-up will, we expect, support this suggestion.