An Extensive Tail Sign in Primary Thoracic Myxofibrosarcoma: A Case Report

Myxofibrosarcoma is a malignant soft tissue tumor of fibroblastic origin, occurring mainly in the extremities but extremely rarely in the thoracic trunk. Myxofibrosarcoma typically appears as a slow-growing, painless mass but features a frequent local recurrence due to microscopic extension beyond visible margins. On MRI, the "tail sign"-which indicates subtle spread along the fascial plane-is known to be a potential risk factor for recurrence.

The patient was a 73-year-old woman complaining of continuous right back pain. Chest CT showed a poorly contrast-enhanced mass involving the 5th and 6th right ribs, as well as a separate nodule. The biopsy confirmed a diagnosis of myxofibrosarcoma. The mass exhibited hypointensity on T1-weighted images and hyperintensity on T2-weighted images on MRI; on contrast-enhanced T1-weighted images and STIR images, a tail sign extending toward a small satellite nodule was observed. The patient underwent an extended resection involving the 5th through 7th ribs. A total of 61.2 Gy radiation was irradiated to the paravertebral region neighboring the tumor where the surgical margin was poor. A local recurrence was detected in the anterolateral region of the tumor resection site 5 months after surgery. The patient was treated with sequential chemotherapy using doxorubicin, eribulin, and pazopanib and is alive at 26 months after surgery without distant metastasis.

The current case exemplifies the aggressive local behavior of thoracic myxofibrosarcoma, especially when a long tail sign appears.