Jejunal metastasis of knee myxofibrosarcoma causing small bowel obstruction: a case report

Introduction and importance: Myxofibrosarcoma (MFS) is one of the most common soft tissue sarcomas (STS) of the extremities and is characterized by a high rate of local recurrence and the potential for distant metastasis. Pulmonary dissemination is the most frequently observed metastatic pattern, whereas gastrointestinal involvement remains exceptionally rare. Presentation of the case: We report the case of a 40-year-old woman previously treated for an MFS of the right knee. Two years after the initial surgery, she developed a local recurrence that was surgically resected. Staging investigations subsequently revealed synchronous pulmonary and hepatic metastases, and systemic chemotherapy was initiated (doxorubicin, nine cycles, partial response). Two years later, the patient presented with acute abdominal pain and signs of intestinal obstruction. Computed tomography demonstrated a large jejunal mass measuring 94 × 76 mm, associated with upstream small bowel dilatation. Emergency exploratory laparotomy revealed a 10 cm jejunal tumor causing luminal obstruction, moderate ascites, and an omental metastatic nodule. Segmental small bowel resection with primary anastomosis was performed. Histopathological examination confirmed a metastatic MFS (FNCLCC grade 2) with associated peritoneal metastases. The postoperative course was uneventful, and the patient was referred for further oncologic management. She was followed for 18 months after the index surgery, during which she developed hepatic and peritoneal disease progression, which was treated with second-line chemotherapy, before she was lost to follow-up. Clinical discussion: Gastrointestinal metastasis from MFS is exceptionally rare, and involvement of the jejunum has not, to the best of our knowledge based on a structured literature search, been previously reported. The mechanism of spread could not be established with certainty in this case; the concomitant finding of peritoneal disease suggests that hematogenous seeding and peritoneal implantation may both have contributed, rather than a single, purely hematogenous pathway. These findings support considering gastrointestinal metastasis in the differential diagnosis of acute abdominal symptoms in patients with a history of STS, even in the absence of prior digestive symptoms. Conclusion: Jejunal metastasis from MFS is extremely uncommon and may present with acute surgical complications such as bowel obstruction. Awareness of this unusual metastatic pattern is important when evaluating patients with a history of soft-tissue sarcoma who present with acute abdominal symptoms. Surgical management remains crucial for symptom relief and diagnosis in the context of advanced metastatic disease.