A 52-year-old woman presents with a 3-month history of painful oral erosions and several flaccid blisters on her chest and back that rupture easily, leaving shallow erosions. She reports burning mouth pain that makes it difficult to eat. On exam, gentle lateral pressure on normal-appearing skin causes the epidermis to shear off (positive Nikolsky sign). A skin biopsy is obtained.

Which of the following histopathologic findings is most likely on light microscopy, and what immunofluorescence pattern would be expected?