[An example of metastasis to the iliopsoas muscle from sigmoid colon cancer]

Even though skeletal muscle, making up about 40% of body weight, is the largest organ in the human body, metastasis from malignant lesions is rare. Among reports of metastasis, those involving the iliopsoas muscle are numerous but few reports involve resection. Reported here is one example we experienced where metastasis developed in the iliopsoas muscle following colectomy, resection was then made possible by radiotherapy and chemotherapy. The case involved a 71-year- old male in which a Hartmann procedure was performed for sigmoid colon cancer. The pathology was Type 3 (8 × 7 cm, adenocarcinoma( mod), ss or more, ly1, v1, n0, ow(-), aw or ew(+), stage II). Upon additional sampling, thermal degredation of neoplastic cells was shown and outpatient oral UFT was performed. Five years following surgery, lymphoadenopathy was noted in the area of the left iliac artery upon US and CT. PET showed a probable metastasis to the left iliopsoas muscle. Early esophageal and stomach cancer were diagnosed by GFT. The esophageal cancer was located 30-32 cm from the incisors, unstained, Borrmann type 1, penetrating deeper than the muscularis propria. Biopsy revealed a diagnosis of tubular adenocarcinoma. ESD was performed for the esophageal cancer and one month later, a total gastrectomy D1+β was performed. During surgery, the iliopsoas muscle tumor was determined to be large and impossible to resect. Radiotherapy of 10MV X-ray, 8 fields, 65-70 Gy/26 times for 6 . 5 weeks was performed for residual tumor but had no effect on tumor size. Fifteen courses of FOLFOX+bevacizumab were then performed. The tumor was markedly reduced in size, unidentifiable upon CT but showed slight uptake on PET and resection of the suspected residual tumor was performed. Histologically, atypical cells were shown in scarred muscle and connective tissue, however, degradation by chemotherapy was high. Residual tumor at resection margins was found, findings consistent with metastasis form sigmoid colon cancer. Taking into account the age and condition of the patient following surgery, chemotherapy was changed to S-1. Currently, 5 months after resection, there has been no recurrence.