A first described chest wall metastasis from colon cancer demonstrated with (18)F-FDG PET/CT

It is well known that, haematogenous colon cancer metastases are most commonly found in the liver, less likely in the lungs through the paravertebral venous system and rarely in other organs. Sporadic clinical cases of colon cancer metastases to the abdominal wall, the thyroid or the adrenal glands have been reported. Here, we present an uncommon case of chest wall metastasis from colon cancer demonstrated with 2-fluoro [fluorine-18]-2-deoxy-D-glucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT). A 52 years old female patient was examined after she felt a swelling mass above her left breast. Tumor makers, such as serum cancer embryonic antigen (CEA) 146.22kU/L (normal range:0.00~37.0kU/L) and CA19-9 (258.16μg/L (normal range:0.00~10.0μg/L) and neuron-specific enolase (NSE) 78.2 (normal range: 0.00~17.00) were abnormally high. Chest CT revealed the soft tissue density mass on the left anterior chest wall with invasion of left 4th rib, and CT-guided biopsy showed a poorly differentiated adenocarcinoma of unkown origin. The patient was then referred for the (18)F-FDG-PET scan which was performed one hour after the intravenous injection of 370MBq of (18)F-FDG (Discovery Camera, VCT, GE, USA) and showed in addition to the chest mass, abnormal (18)F-FDG accumulation in both lungs, left supraclavicular and peritoneal lymph nodes. Furthermore, high (18)F-FDG uptake was detected in the sigmoid. Pathology findings from colonoscopy confirmed that this was a sigmoid colon adenocarcinoma. So far, chest wall metastasis from colon cancer as an initial finding has not been reported. Usually, an initial chest wall mass is hardly suspected to be a colon cancer metastasis. Abnormal serum tumor markers such as CEA and CA19-9 supported the diagnosis of a gastrointestinal adenocarcinoma. In our case, we found high serum NSE and normal findings of bowel wall on the CT scan, thus without the positive (18)F-FDG findings, one would probably consider as first diagnosis: chest wall metastasis from lung cancer, or a neuroendocrine tumor. The unusual finding in this case was that on the CT images there was no obvious local density of the intestine, no bowel wall thickening, or suspicious nodular lesions. Segmental (18)F-FDG accumulation seen in the sigmoid colon had early maximum standardized uptake value (SUV(max)) 7.3 and in 1h delayed estimation, 8.1. Colonoscopy showed that the (18)F-FDG-avid area at the colon was circular and thickened. "Hot" lesions found in both lungs, the supraclavicular and retroperitoneal lymph nodes by (18)F-FDG PET/CT scan were considered to be most probably metastases from colon adenocarcinoma. In conclusion, PET as a rather simple procedure and less dependent on bowel preparation diagnosed the primary colon cancer, its metastases and specifically a first described chest wall metastasis, while CT alone did not show the primary tumor.