A = the neoplasm was composed of atypical non-cohesive cells individually arranged in a single-file linear pattern immersed in a fibrous stroma (hematoxylin and eosin stain, original magnification x200).
B = single-file linear cords of atypical cells with plenty of pale cytoplasm and typical lack of cohesion were observed throughout the lesion (hematoxylin and eosin stain, original magnification x400).
C = immunohistochemical staining for low-molecular-weight keratin confirmed the nature of the neoplastic cells (original magnification x200).
D = strong estrogen receptor, immunohistochemical expression in many neoplastic cells (original magnification x200).