A 62-year-old man undergoes ultrasound of the abdomen for evaluation of persistent hypertension. The study reveals a heterogeneous solid renal mass marked **A** in the diagram, measuring 5.5 cm, with internal hypoechoic foci and distortion of the renal contour. Color Doppler shows internal vascularity. The patient reports no flank pain or hematuria. Which of the following statements about the structure marked **A** is most consistent with the diagnosis of renal cell carcinoma?