All cases were stained for INSM1 (clone A8, Santa Cruz Biotechnology, Santa Cruz, CA, diluted 1:100) using an automated immunostainer platform (BenchMark AutoStainer, Ventana Medical Systems, Tucson, AZ, USA). The intensity (weak to strong) and the percentage of positive tumor cell nuclei were recorded. The cut off for a positive reaction was set at 5% of tumor cells, as previously reported [22 (link)]. Pancreatic tissue, representing appropriate positive (Langerhans islets) and negative (acinar cells) controls, was included in each IHC run.
When missing from the file, CGA (clone LK2H10, Ventana, prediluted) or SYN (clone SP11, Ventana, prediluted) were tested using the BenchMark AutoStainer. Both markers were classified as (i) diffusely positive if present in more than 50% of tumor cells, (ii) focally positive if present in < 50% of tumor cells, and (iii) absent if no staining was observed.
When missing from the file, CGA (clone LK2H10, Ventana, prediluted) or SYN (clone SP11, Ventana, prediluted) were tested using the BenchMark AutoStainer. Both markers were classified as (i) diffusely positive if present in more than 50% of tumor cells, (ii) focally positive if present in < 50% of tumor cells, and (iii) absent if no staining was observed.