EP251 - A Rare Case of Metastatic Myxofibrosarcoma to the Right Colon

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Purpose/Background: Myxofibrosarcoma is a connective tissue malignancy which typically presents in the extremities of the adult population. This subtype of sarcoma has higher rates of local recurrence and positive margins due to its infiltrative pattern of growth. Myxofibrosarcoma metastasizes in 20-35% of cases and usually spreads to the lungs, lymph nodes, and bone. Gastrointestinal metastasis, particularly to the colon, is exceedingly rare based on current literature.

Methods/Interventions: A 76-year-old male with a past medical history of hypertension, unprovoked deep vein thrombus on anticoagulation, prostate cancer in remission, and left flank myxofibrosarcoma in 2021 that was treated with wide local excision and local radiation due to close margins. The final pathology of the wide local excision resulted as a myxofibrosarcoma, high-grade, forming an 8.8 cm mass. Years later, he presented to the emergency department with abdominal pain and decreased flatus and bowel movements for several days. A CT abdomen and pelvis showed concern for a 4cm cecal mass not noted on previous surveillance imaging. These findings were concerning for metastatic disease of the patient’s previous myxofibrosarcoma. The patient was admitted and resuscitated. During his hospitalization, a CT-guided biopsy was performed of the mass which confirmed the diagnosis of myxofibrosarcoma. After a tumor board discussion, primary resection of the mass was recommended. A colonoscopy demonstrated a cecal mass close to the ileocecal valve and no other lesions. He underwent an uncomplicated robotic right colectomy with primary intracorporeal anastomosis. He recovered appropriately and was discharged to a subacute rehab facility on postoperative day seven.

Results/Outcomes: The median time for recurrence of myxofibrosarcoma is 21 months. Even though this patient underwent post-operative radiation, current data demonstrates that radiation does not affect the metastatic potential of the tumor. The metastatic potential of these soft tissue sarcomas is more dependent on the pathologic grade of the tumor, which was high for this patient’s primary tumor. High-grade myxofibrosarcomas have a metastasis rate of 18-47%. Other risk factors associated with increased metastatic potential in soft tissue sarcomas that have been treated with radiation include a tumor size greater than 5 cm; location in the head, neck, or deep trunk; and a patient age greater than 64 years. This patient had all these concerning features for metastasis. However, the colon is an extremely atypical location.

Conclusion/Discussion: Myxofibrosarcoma is a common soft tissue tumor. Given this patient’s high-grade primary tumor, surveillance is crucial to favorable outcomes and quickly identifying metastasis. This is the second colonic metastasis of myxofibrosarcoma documented in the literature. While this location is rare, it is important to have an awareness of this potential to properly care for these patients. Special attention should be given when patients with a history of myxofibrosarcoma with new-onset gastrointestinal symptoms. Further studies should be completed as to what factors influence the atypical spread of these sarcomas.