Pathologists use non-reactive to describe the results of a test called immunohistochemistry. This test allows pathologists to see groups of cells according to the chemicals those cells are making. Most of these chemicals are proteins.
Pathologists can use immunohistochemistry to look for hundreds of different kinds of chemicals. Non-reactive means that the group of cells being examined were not making the chemical described in your report.
Some pathology reports will describe non-reactive cells as negative. The opposite of non-reactive is reactive or positive.
“The tumour cells are non-reactive for S100” – In this example immunohistochemistry was performed to look for a protein called S100 and no S100 was seen in any of the tumour cells.