A 6-year-old boy is brought to the pediatric clinic with progressive periorbital swelling and generalized edema over the past week. His parents have also noticed that his urine appears frothy. He has no fever, hematuria, or recent infections. On examination, blood pressure is normal, and there is pitting edema in his lower limbs. Laboratory findings show 3+ proteinuria, hypoalbuminemia (2.0 g/dL), and hyperlipidemia (total cholesterol 280 mg/dL). Serum creatinine is normal. Which of the following findings is most characteristic of this disease on kidney biopsy?
