Which histological marker is indicative of neuroendocrine tumors?

Chromogranin A is a key histological marker for neuroendocrine tumors (NETs). This protein is secreted by neuroendocrine cells, which are characterized by their ability to produce and secrete hormones and neuropeptides. The presence of this marker is particularly useful in both the diagnosis and monitoring of neuroendocrine neoplasms, such as carcinoid tumors and pheochromocytomas.

In neuroendocrine tumors, chromogranin A levels can be elevated, and its detection through immunohistochemical staining can assist pathologists in differentiating these tumors from other types of neoplasms. The specificity of chromogranin A for neuroendocrine cells makes it a valuable tool in the diagnostic workup.

The other markers listed are associated with different types of cells or neoplastic processes. For instance, S100 protein is often linked to melanocytes and glial cells, cytokeratins are primarily markers for epithelial cells, and CD20 is a B-cell marker. Therefore, the unique association of chromogranin A with neuroendocrine tumors underscores its importance as a histological marker in this context.