Post-radiation soft tissue sarcomas are recognized as rare complications of radiation therapy. The most common
type of post-radiation soft tissue sarcoma is a malignant fibrous histiocytoma (MFH), which originates from
mesenchymal cells with a predominance of histiocytes and fibroblasts. The two most common sites of occurrence
for post-radiation soft tissue sarcomas are the chest wall and pelvic cavity. Post-radiation colorectal MFHs are
extremely rare and all of the reported cases of post-radiation sarcomas have occurred >3 years after radiation therapy.
Recently, we managed a case of colorectal MFH which developed in a 48-year-old male who had undergone a
low anterior resection for rectal adenocarcinoma and had received chemoradiotherapy as adjuvant treatment. Twelve
months after radiotherapy, a 4 cm mass was detected 8 cm superior to the anastomosis site on colonoscopic
examination. A soft tissue sarcoma was suspected on pathologic examination of the biopsy specimen. Therefore,
he underwent a Hartmann’s operation and the final pathologic finding revealed MFH with a storiform pattern of
tumor cells composed of pleomorphic, multinucleated giant cells. This is the first case of MFH that had a latency
period <3 years (i.e., 1 year) between the time of radiotherapy and diagnosis