Figure 5. (A) Hematoxylin and eosin at 60× magnification showing tumor cells exhibiting small nucleoli without prominent nuclear atypia, mitotic activity, or necrosis. (B) Chromogranin at 20× magnification: diffuse positive staining was observed in tumor cells, confirming neuroendocrine differentiation. (C) Synaptophysin at 20× magnification: tumor cells demonstrated strong and diffuse positivity, further supporting neuroendocrine lineage. (D) Adrenocorticotrophic hormone (ACTH) at 20× magnification: immunoperoxidase staining for ACTH shows positive labeling in tumor cells. (E) Ki-67 at 20× magnification: the Ki-67 proliferation index of 8% classifies this tumor as a World Health Organization grade 2 neuroendocrine tumor.