Ultrasound
Typically hypoechoic. May show a lobulated distinct border +/- posterior acoustic enhancement with through transmission.
Ultrasound is also useful in guiding biopsy (both FNAC and core biopsies) but needs to be carried out with care to avoid facial nerve damage 8,9.
CT
Smoothly marginated or lobulated homogeneous small spherical mass is the most common appearance. When larger they can be heterogeneous with foci of necrosis. Small regions of calcification are common 1,10.
When the tumour is small, the enhancement tends to be prominent. In larger tumours enhancement is less marked, but can demonstrate delayed enhancement 10.
MRI
They are commonly seen as well-circumscribed and homogeneous when small. Larger tumours may be heterogeneous:
• T1: usually of low intensity
• T2
o usually of very high intensity (especially myxoid type) 6
o often have a rim of decreased signal intensity on T2-weighted images representing the surrounding fibrous capsule
• T1 C+ (Gd): usually demonstrates homogeneous enhancement