Extraspinal malignancies found incidentally on lumbar spine MRI: Prevalence and etiologies

The lumbar spine magnetic resonance imaging (MRI) is the commonly used image modality for evaluation of patients with low back pain or sciatica. Some extraspinal malignancies are found incidentally on routine lumbar spine MRI studies which are more important than the spinal findings. Between January 2010 and December 2011, we screened 5104 patients who experienced low back pain or sciatica and underwent routine non-enhanced MRI examinations, and 215 of them also received CT scans within one year. Patients with extraspinal malignancies seen in both CT and MRI were enrolled and analyzed. A total of 26 patients and 28 extraspinal malignancies were enrolled (17 male and 9 female, age range: 33-84 years old, mean age: 55.7 years old). The incidental extraspinal malignancies included 9 paraaortic lymphadenopathies, 7 renal tumors, 5 iliac bony lesions, 4 adrenal tumors, 2 liver tumors, and 1 colon tumor. The prevalence of newly diagnosed extraspinal malignancies was 0.5%. Among the 26 patients with newly diagnostic extraspinal malignancies, 12 (46%) of them did not have coexisting spinal metastases and the most common etiologies were renal cell carcinoma and iliac bony metastases. The possible reason may be due to these lesions induce back pain similar to degenerative spinal disease. Extraspinal structures should be carefully and systemic evaluated on routine lumbar spine MRI, especially if the spinal findings cannot explain the symptoms of the patients.