CASE OF THE MONTH
Singapore General Hospital
A 34 years old female had presented with a lump at the radial aspect of her thumb. The lump had been increasing in size over the past year, with pain felt when the thumb is flexed/extended. Tingling sensation at the thumb was felt occasionally. What could be the diagnosis?
Figure 1: Longitudinal (LS) view of the lesion. It is well-defined, hypoechoic peripherally with hyperechoic central region, and posterior enhancement seen.
Figure 2. Transverse (TS) view of the lesion.
Figure 3. Colour Doppler demonstrates hypervascularity within the lesion.
Figure 4. Colour Doppler demonstrates hypervascularity within the lesion.
Majority of the peripheral nerve tumours are benign. Some of the more common lesions that can be seen include schwannoma and neurofibroma.
Typical sonographic appearances of a benign peripheral nerve tumour include1,2:
- Well-defined hypoechoic nodule
- Hyperechoic centre with hypoechoic periphery seen on transverse imaging (“target sign”) [due to a central fibrocollageneous region and a peripheral myxomatous region]
- Lies in continuity with the peripheral nerve. Schwannomas tend to have nerve fibres entering the lesion at eccentrically, while neurofibromas tend to have the nerves entering the lesion centrically.
- Posterior enhancement of the nodule
- Increased internal vascularity
- Reynolds, DL, Jacobson, JA, Inampudi, P, Jamadan DA, Ebrahim, FS &Hayes, CW 2004, ‘Sonographic characteristics of peripheral nerve sheath tumours’, AJR, 182:3, pp. 741-744
- Ali, ZS, Pisapia, JM, Ma, TS, Zager, EL, Heuer, GG & Khoury, V 2015, ‘Ultrasound evaluation of peripheral nerves’, World Neurosurgery, doi:10.1016/j.wneu.2015.10.005