Primitive oocyte-like cells (arrows) in the ovarian surface epithelium above the autofluorescent necrotic malignant tissue of a patient with serous papillary adenocarcinoma. (A, D) SSEA-4-positive cells (green). (B, E) SOX-2-positive cells (red). (C, F) Non-stained cells. (A, B, C: fluorescent and light microscopy, magnifications 400×; D, E, F: fluorescence and light microscopy, magnifications 1000×).