Case report: recurrence of soft tissue MFH in bone due to minute intravenous tumor emboli detected by MRI.

We recently encountered a case with local recurrence of malignant fibrous histiocytoma (MFH) in the bone after wide resection, caused by minute intravenous tumor emboli which were retrospectively detected in MR imaging. The patient was a 69-year-old woman who initially noticed a mass in her left thigh. The tumor was diagnosed to be MFH, therefore a wide resection was performed; although the tumor was closely attached to the periosteum, it was not difficult to dissect the tumor subperiosteally from the cortex of the femur. The patient received postoperative brachytherapy, but no chemotherapy. Two years later, the tumor recurred with bony destruction of the femur. We reviewed the pre-operative films obtained by various imaging modalities, as well as the histology of the primary tumor, and found minute intravenous tumor emboli in the MR imaging obtained before surgery. Tumor emboli were also observed histologically in the small vessels of the surgically resected tumor. Such intravenous tumor emboli have recently been implicated in the development of regional bone metastasis near the site of the primary lesion in cases of malignant soft tissue tumors. Therefore, we concluded that the tumor recurrence in our case was caused by small tumor emboli invading the perforating veins of the femur. It is therefore emphasized that MR images should be carefully reviewed for the presence of such intravenous tumor emboli before surgery in cases of high-grade malignant sarcomas. As at the time of writing, our patient remains alive and disease-free, with no evidence of any local recurrence or distant metastasis after wide tumor resection for the recurrent tumor.