2. Margins and Imaging

Modern imaging facilitates successful functional limb salvage, often with margins that would be classified as marginal in the Enneking system [13]. Precisely this distinction is important in the light of sparing as much tissue as possible for preferable functional outcomes [14]. Magnetic resonance imaging (MRI) is the imaging tool most sensitive and accurate to assess margins in STS. On conventional MRI, there are several recognized features related to margins infiltration and subsequent increased risk of LR after surgical excision.

Recent technical development of imaging analyses and the increasing request for evidence-based medicine, led to a greater use of quantitative imaging. One of the most promising tool is radiomics: it is a quantitative tool applicable to imaging, which aims at enhancing the existing data by means of advanced mathematical analysis. Through mathematical extraction of the spatial distribution of signal intensities and pixel interrelationships, this tool quantifies textural data by using analysis methods from the field of artificial intelligence [24].

3. Margins Assessment

A recent consensus practice guideline remarked that “no available evidence-based data addressed how to adequately assess margins” [3]. Pathologists assess surgical resection margins by submitting more sections from margins that are close or concerning on gross inspection. However, careful gross assessment of surgical resection margins can be misleading. Therefore, microscopic examination of six to eight perpendicular sections in total from all margins <2 cm in width is a practical compromise and a reasonable recommendation [29].

4. Comparison between Classifications

Gundle et al. [39] by direct comparison of three schemes (R, R+1 and TMCC classifications) concluded that the traditional R classification best determined the risk of LR, but TMCC provides additional stratification of positive margins that may aid in the surgical planning. Kainhofer et al. [40] compared different classifications of resection margins (R and R+1 classifications) on LR and found out that margin status according to both classifications was a significant prognostic factor for LR. However, they observed that a R0 margin determined by the UICC classification is a better discriminator for LR than R0 resections according to the R classification. A higher percentage of positive resection margins naturally results by applying the stricter definition of the UICC classification [40]. This indicates that R1 resections as defined by the UICC-classification pick out more patients with high risk of LR than R1 resections according to the R-classification would do.

5. Margins Width

Most of the series observed that tumor resection with a gross positive margin are accompanied by unacceptably high rates of LR [41,51,55,56]. However, a solely positive or negative status of a margin, as clear but close margins and broader margins should not be considered equal in their risk to the patient [8]. The real question is what constitutes an “optimal” margin? 

Adequate margin has been described in several ways, ranging from adjectives like a radical, wide, or close [6] until negative (>0 mm) margin [52,57], up to 3 cm [53,58], or even 5 cm [53]. 

Two different series reported that a minimum 5 mm margin is adequate if no adjuvant radiation therapy (RT) is administered, but it can be reduced to 1 mm with post-operative RT [29,65]. Sadoski et al. [66], as well as many other series [10,13,44,47,52,60,66], suggested that patients who have microscopic positive margins have lower rates of LR as long as the surgical excision is coupled with adjuvant RT. On the other hand, another series [44] observed that positive margins were associated with lower local control despite the utilization of adjuvant RT, suggesting negative margins remains a primary objective for all treatment options. 

6. Margins in Specific STS Histotypes

Specific STS subtypes such as myxofibrosarcoma (MFS) and undifferentiated pleomorphic sarcoma (UPS) frequently present with an infiltrative growth pattern [19,20,42,48,49,67]. They have an increased likelihood of LR irrespective of the surgical margins [68]. Therefore, it is crucial to analyze the entities separately and to assess the prognostic significance of treatment-related factors for every histologic subset specifically. A resection margin of 2 cm away from the end of the radiological tumor infiltration would be the ideal margin because the vast majority of cases could achieve broad histological in infiltrative sarcomas resection seems to be overstated. Nevertheless, such a broader resection can increase the demand for plastic reconstruction surgery, risk of wound complication, and functional deterioration.