Fontana-Masson stain

Fontana-Masson stain is a silver based histochemical stain. It is used for two purposes: (1) to demonstrate melanin and (2) to demonstrate argentaffin granules in neuroendocrine cells. The principle of the stain lies in reduction of silver nitrate to metallic silver which appears black.

Diagnostic utility (the list is not exhaustive)

1. Demonstration of melanin pigment in normal melanin containing cells and melanocytic neoplasms, both benign and malignant
2. Demonstration of melanin in the cell wall of Cryptococcus neoformans, both typical and capsule-deficient
3. Demonstration of argentaffin granules in normal neuroendocrine cells and neuroendocrine neoplasms