**Abstract**

Adenosine triphosphate (ATP) and other nucleotides and nucleosides, such as adenosine, are signaling molecules involved in many physiological and pathophysiological processes. The group of cell and tissue responses mediated by these molecules is known as purinergic signaling. Ecto-nucleotidases are ectoenzymes expressed at the cell membrane that act sequentially to efficiently hydrolyze extracellular ATP into adenosine, and they are key elements of this signaling. There is growing interest in studying these enzymes in relation to various pathologies, especially those with an inflammatory component such as cancer. This review summarizes the main protocols for the study of the expression and in situ activity of ectoenzymes in tissue slices and cultured cells.

**Keywords:** nucleotidase, in situ histochemistry, CD39, CD73, lead staining
