A 52-year-old woman comes to the clinic for evaluation of painful oral sores and new skin lesions. Over the past 3 weeks, she has developed several flaccid blisters on her chest and back that rupture easily, leaving shallow erosions. She reports significant burning pain but minimal itching. Examination shows multiple irregular erosions on the buccal mucosa and soft palate. Gentle lateral pressure on normal-appearing skin adjacent to a lesion causes the superficial epidermis to shear off. A punch biopsy is obtained from the edge of an intact blister, and direct immunofluorescence is performed on perilesional skin.

Which of the following histopathologic/immunofluorescence findings is most likely present?