Which immunohistochemical markers are commonly positive in neuroendocrine tumors such as small cell lung carcinoma?

• A. Chromogranin and Synaptophysin
• B. GFAP and S100
• C. CD20 and CD3
• D. Desmin and Myogenin

Answer: (A)

Neuroendocrine tumors show markers that reflect their secretory granule and vesicle biology. Chromogranin A is stored in secretory granules of neuroendocrine cells, and Synaptophysin is a presynaptic vesicle protein; both are commonly and robustly positive in neuroendocrine tumors like small cell lung carcinoma. Their presence supports neuroendocrine differentiation and helps distinguish these tumors from others.

Markers like GFAP and S100 point to glial or neural crest–derived lineages, not specifically neuroendocrine tumors. CD20 and CD3 identify B and T lymphocytes, respectively, and Desmin and Myogenin indicate muscle differentiation (myogenic tumors). So Chromogranin A and Synaptophysin are the best indicators for neuroendocrine origin in this context.