A 39-year-old female patient presented with a 3-year history of lower back pain which had not been alleviated by pain treatment combined with physiotherapy. Radiological findings were normal with the exception of a cystic paravertebral tumor in the left retroperitoneum. The cyst was primarily regarded as a coincidental finding because no criteria for malignancy were present. Magnetic resonance tomography, however, the cyst showed a progressive increase in size and the pain remained unchanged so that surgical resection was performed. The histopathological examination showed a lymphangioma and the pain was nearly completely resolved after surgery.