In Group A, 4 from 17 samples (three NETG3s and one NETG2 (an insulinoma and a MEN1 syndrome tumor)) displayed staining for SOX9, albeit with a low and heterogenous pattern, unlike Group B positive tumors (Fig. 4d and Additional file 2: Fig. S4f). Here, SOX9 is linked to multiple endocrine neoplasia type 1.