Molluscum Contagiosum in a Child

A 5-year-old immunocompetent boy presents with a 6-week history of multiple asymptomatic skin lesions over the trunk, axillae, and flexures. He attends swimming classes and shares towels with his sister who has similar lesions. On examination, there are 25–30 discrete, pearly white to flesh-colored, firm, dome-shaped papules measuring 2–5 mm, each with a characteristic central umbilication containing a cheesy white core. The lesions shown marked as **A** in the diagram are examined histopathologically. Which of the following is the pathognomonic histological finding in these lesions?