RESUMEN
BACKGROUNDS: Cancer metastasis to skeletal muscle is very rare. Lung cancer, renal cell carcinoma and malignant melanoma have been reported as the most frequent primary tumours. Diagnosis of muscle metastasis from other primary cancer sites is more than problematic. CASE: In this paper we report a case of metastasis of colorectal cancer in a 44-year-old man who underwent left-sided hemicolectomy due to the tumour mass in his left colic flexure followed by liver metastasectomy and cryocautery of the non-resectable metastasis in the VII segment. Subsequently, the patient was treated with two lines of chemotherapy. However, shortly after initiation of the second chemotherapy line he started to suffer from unbearable pain in the lumbosacral region. Neither a whole spinal cord MRI nor abdominal CT scan and scintigraphy explained the origin of the pain. Finally, PET/CT examination clarified the origin of the pain and showed massive hypermetabolic metastatic lesions in the muscles, further confirmed by autopsy. CONCLUSION: Thus, among the different imaging techniques, FDG PET/CT enables the detection of metabolically highly active tumour cells, undetectable by other conventional imaging means.