Paravertebral abscesses are usually caused by Staphylococcus aureus, and often affect older people with diabetes mellitus or immunosuppression. We report a huge lumbar abscess caused by Escherichia coli in an 81-year-old woman with diabetes and melanoma metastasis. Lumbar vertebra and surrounding soft tissues were involved by the Gram-negative infection, and imaging features were indicative of malignant condition. Diagnosis was established by images of magnetic resonance, histopathology, and bacterial culture from abscess fluid. This condition poses diagnosis challenges and seems to be increasing in frequency. Reports of case studies might enhance the suspicion index of primary care physicians about this entity.