is fluid fluid level in osseous lesions a diagnostic clue

1. Abstract Fluid-Fluid Level (FFL) is a non-specific cross-sectional imaging finding described in de novo and secondary Aneurysmal Bone Cysts (ABC) and in a variety of conditions including benign and malignant tumours. This is a review of osseous lesions showing FFL and the relative diagnostic value of the sign based on our experience and the relevant literature. We studied 35 cases of tumours and tumour like lesions having FFL. The imaging features were analysed with respect to single or multiple, occupancy percentage, uniformity, septae and the ratio of the largest FFL to the total tumour length. The percentage of occupancy of FFLs is an important clue to differentiate benign from malignant lesion with only exception of TOS. Uniformity of FFLs and irregularity/ nodularity in septum should also be studied which add to the diagnostic value. Additionally, signal intensity of FFLs in T1W, T2W/STIR sequences can enhance diagnostic accuracy. 2. Keywords: Aneurysmal Bone Cyst; Fluid-Fluid Level; Telangiectatic Osteosarcoma