An assessment of fluid–fluid levels on magnetic resonance imaging of spinal tumours

To assess the degree of fluid–fluid levels on MRI in spinal tumours compared with final diagnosis, and the outcome of needle biopsy in such cases.

Retrospective review of patients with a spinal tumour that contained fluid–fluid levels. Data collected included age, sex, spinal location, and final diagnosis. The outcome of needle biopsy was investigated.

Forty-two patients were included (19 males; 24 females; mean age 27.5 years, range 5–80 years), the commonest diagnoses being aneurysmal bone cyst (n = 25; 59.5%) and metastasis (n = 5; 11.9%). All patients with a malignant diagnosis were > 50 years of age apart from 2 who had metastases from a known primary cancer, while all patients apart from 1 with aneurysmal bone cyst were < 35 years of age. Needle biopsy was undertaken in 29 cases (69%) and diagnostic in 18 (62%). Patients with FFL occupying > 2/3 of the lesion were significantly more likely to have an aneurysmal bone cyst (p = 0.008) while those with FFL occupying < 2/3 of the lesion were more likely to have a malignant tumour (p = 0.001). The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of > 2/3 FFLs occupying the lesion were 97.1%, 75%, 94.3%, 85.7%, and 92.9% respectively for differentiating a benign from a malignant spinal tumour.

Children and younger adults with spinal lesions containing > 2/3 FFLs were very unlikely to have malignancy. However, in patients > 50 years of age or those with lesions containing < 2/3 FFLs, a malignant lesion is much more likely.