A 6-year-old boy presents with facial puffiness that is most prominent in the morning around his eyes and has been worsening over 2 weeks. By evening, swelling develops around his ankles that leaves an indentation when pressed. Blood pressure is 98/62 mmHg. Physical examination shows periorbital edema and bilateral pitting edema to the ankles.
Laboratory studies:
- Serum albumin: 2.4 g/dL
- Serum creatinine: 0.6 mg/dL
- 24-hour urine protein: 4.2 g
Urinalysis shows 4+ protein with no blood or red blood cell casts.
Which of the following findings on urine microscopy would most strongly support the suspected diagnosis?