Endometriomas on ultasound appear as: (A) Solid with diffuse internal low-level echoes., (B) Solid with focal internal low-level echoes., (C) Cystic with diffuse internal low-level echoes., (D) Cystic with focal hyperechoic internal echoes.
Answer is C. Endometrioma  classically is cystic with homogenous, low-level internal echoes, i.e ground-glass echogenicity.