This paper presents an introduction to the cellular signaling mechanism governed by the balanced action of protein tyrosine kinases (PTK) and protein tyrosine phosphatases (PTP) by phosphorylation / dephosphorylation of tyrosine residues in proteins. For many years PTK were the main targets for the development of anticancer drugs and today many PTK inhibitors are already widely used in the cancer treatment. Inhibitors of PTP are still in the development stage because of misconceptions about this family of enzymes. Thus, this review seeks to clarify some important points that justify the current interest in PTP as a target in cancer treatment. An introductory description of the classification is made, together with a discussion on structure and PTP mechanism of action with particular focus on SHP family composed of two PTP: SHP-1 and SHP-2. This paper discusses the effects of over expression or gain of function mutations occurred in SHP-2 in the emergence and progression of cancerous state by activation of the RAS / ERK. Finally, some SHP-2 inhibitors that have been discovered to date are presented.