Which marker is included in the general neuroendocrine IHC panel along with chromogranin and synaptophysin?

• A. S-100
• B. Melan-A
• C. FOXL2
• D. CD10

Answer: (A)

The main idea here is how neuroendocrine tumors are profiled with immunohistochemistry. Chromogranin A and synaptophysin are classic markers that confirm neuroendocrine differentiation by highlighting neuroendocrine granules and cell membranes, respectively. A common additional marker in this context is S-100, which is used to identify sustentacular cells that surround tumor nests in paragangliomas and pheochromocytomas. The presence of these S-100–positive sustentacular cells around chromogranin/synaptophysin–positive nests supports a paraganglioma/pheochromocytoma diagnosis and helps distinguish these tumors from other non-paraganglionic neuroendocrine neoplasms.

Melan-A is a melanocytic marker, not part of the neuroendocrine panel. FOXL2 is a marker relevant to granulosa cell tumors, not neuroendocrine tumors. CD10 has various uses but does not serve the same diagnostic role in standard neuroendocrine panels as S-100 does for identifying sustentacular cells in paragangliomas.