Alcian blue is used in the histology laboratory to demonstrate acid mucins which can be secreted by various connective and epithelial tissue tumors. Acid mucosubstances are stained turquois-blue.
The alcian blue stain is most commonly used on tissue samples obtained from the gastrointestinal (GI) tract and is useful in diagnosing pathological processes such as Barrett's esophagus.
Using alcian blue solutions of varying pH (1.0 and 2.5) also helps differentiate various types of acid mucosubstances.
Alcian blue may be used in combination with the PAS staining procedure, so that both acid and neutral mucins can be demonstrated in the same tissue sample. Alcian blue will stain acidic mucins blue and PAS will stain neutral mucins rose red. This technique is also useful in diagnosing diseases of the GI tract.