ERBB2 and adenocarcinoma: The two cases of HER2‐positive patients who received trastuzumab showed a reduction rate close to the median reduction rate for each grade (Case 1: papillary adenocarcinoma, SUVmax reduction rate 43.9%, histological response Grade 1a; Case 2: moderately differentiated adenocarcinoma, SUVmax reduction rate 69.0%, Grade 2a).