Many surgeons participate in the management of superficial soft tissue masses, and a preoperative incorrect diagnosis frequently results in dismal oncological outcomes. The aim of this study was to identify distinguishing magnetic resonance imaging features between malignant and non-malignant lesions.

The clinicopathological data for 219 patients (men 114; women 105) with superficial soft tissue masses treated from January 2007 to December 2016 in our institution were retrospectively analyzed.

The median age at the first visit was 55.6 years (range 1-90 years). MRI findings of tumor size, margin, lobulation, intratumoral hemorrhage, peritumoral edema, and tumor-fascia relationship were compared with the final histological diagnosis and tumor grade.

Histological diagnosis and tumor grade

Univariate analysis revealed significant relationships between histologically malignant lesions and tumor size ≥5 cm (p = 0.035), positive peritumoral edema (p = 0.031), and tumor-fascia relationship (p<0.001), but not margin (p = 0.107), lobulation (p = 0.071), and intratumoral hemorrhage (p = 0.17).

In addition, using multivariate analysis, the tumor-fascia relationship (p<0.001) and tumor size were significant factors. A significant correlation between tumor-fascia relationship and malignancy (p<0.001) was observed; such a relationship was, however, not observed for tumor grade (p = 0.43).

Tumors measuring ≥5 cm and the tumor-fascia relationship on magnetic resonance imaging are highly indicative of malignancy. When superficial soft tissue masses cross the superficial fascia and form obtuse angles with the fascia, sarcoma should be considered. The tumor-fascia relationship can offer surgeons useful information regarding the status of superficial soft tissue masses.

In primary soft tissue sarcomas, it is expected that high-grade sarcomas would demonstrate locally aggressive behaviors, such as those lesions belong to group 4 and 5 of the Galant classification. However, we could not find a significant association between the tumor-fascia relationship and tumor grade. Thus, tumor grade did not influence tumor-fascia relationship.

In conclusion, tumor size and the tumor-fascia relationship observed on MRI were closely associated with malignancy of superficial soft tissue masses. When primary superficial soft tissue sarcomas cross the superficial fascia and form obtuse angles with the fascia, malignancy should be suspected; metastatic tumors did not present these features.