Which soft tissue masses can be diagnosed on Ultrasound?
Although US findings are often nonspecific for the characterization of soft tissue masses, there are several instances in which US is diagnostic. US is very helpful at differentiating cystic from solid masses. A simple cyst should appear anechoic on US with increased through transmission and thin, nearly imperceptible walls. A mass is solid appearing with heterogeneous or homogeneous hypoechoic internal echotexture. The borders of a mass may be irregular or ill-defined. While a mass may be partially cystic, it should not be diffusely anechoic as with a simple cyst. In the case of a partially cystic mass, there is often irregular or nodular thickening of the walls or internal septations. Finally, a simple cyst should not have vascularity upon color or power Doppler imaging. Masses will often have increased blood flow either diffusely/centrally or at regions of septal/wall thickening. Masses that can frequently be diagnosed under US include: ganglion cyst, parameniscal cyst, lipoma, fat necrosis, peripheral nerve sheath tumor (PNST), and giant cell tumor of the tendon sheath (GCTTS).