Clinical significance of the tail-like pattern in soft-tissue sarcomas on magnetic resonance imaging.

Background: An infiltrating abnormal signal around soft-tissue tumors along the fascial, neurovascular, or musculature plane on magnetic resonance imaging (T2-weighted, gadolinium-enhanced T1-weighted, or short-tau inversion recovery) is recognized as the "tail-like pattern". The tail-like pattern was intensively analyzed in myxofibrosarcoma, but not in other sarcomas. We aimed to answer some key questions about the tail-like pattern such as its incidence and effect on oncological outcomes.

Methods: The presence of the tail-like pattern in 114 soft-tissue sarcomas was evaluated on T2-weighted images or gadolinium-enhanced T1-weighted images, or both. We analyzed the incidence of the tail-like pattern in all cases and in specific histological subtypes. We also assessed the clinical backgrounds of the presence of the tail-like pattern and its impact on achieving adequate surgical margins and oncological outcomes, including local recurrence and overall survival.

Results: The tail-like pattern was detected in 50% of cases. The tail-like pattern was most common in myxofibrosarcoma and undifferentiated pleomorphic sarcoma, and less common in low-grade sarcomas. Trans-compartmental invasion of the tumor and high-grade malignancy were common clinical backgrounds for the presence of the tail-like pattern. The presence of the tail-like pattern significantly inhibits the achievement of preoperatively planned surgical margins despite planning the margins outside the tail-like pattern area. The tail-like pattern was an independent risk factor for local recurrence. The pattern was not an independent risk factor for worse overall survival, although it was a risk factor in univariate analysis.

Conclusion: The tail-like pattern is clinically significant in myxofibrosarcomas and other sarcomas with respect to the preoperative evaluation of malignancy by magnetic resonance imaging, and negatively affects successful resection and oncological outcomes. A more sophisticated modality for the evaluation and clinical management of the tail-like pattern is needed in the future.