ERBB2 and papillary adenocarcinoma: In detail, a progressive increase in the oncoprotein immunoreactivity was observed, from the frequently HER2-negative poorly cohesive histotype (3.5%; Fig. 1A) to MRCs (11.1%), tubular/papillary adenocarcinomas (31.3%; Fig. 1B and C) and HACs (42.9%).