Masson Fontana staining can demonstrate argentaffin granules. Which tissue is used to demonstrate argentaffin granules?

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Masson Fontana is a silver stain used to reveal argentaffin granules, which are stored in certain neuroendocrine (enteroendocrine) cells. These granules contain monoamines such as serotonin and are seen as dark deposits because the cells reduce silver ions themselves (argentaffin reaction) without needing an external reducer.

The classic tissue to demonstrate argentaffin granules is the mucosa of the small intestine, where enterochromaffin cells are abundant. These cells harbor numerous serotonin-containing granules, which react strongly with the Masson Fontana stain, producing a black or brown coloration that highlights the granules.

Liver, spleen, and lymph nodes do not contain these enteroendocrine granules in the typical distribution seen in the small intestine, so they do not show the argentaffin reaction the same way.