Vellucc R, et al. - This review was planned to figure out the most important concepts for the correct diagnosis of breakthrough cancer pain (BTcP) and present some intriguing cases of the management of this condition in clinical practice. For the management of BTcP, a rapid-onset opioid (ROO) seemed the most appropriate therapeutic choice, and in particular, the nasal route of administration proved the quickest and most convenient mode of administration, especially when the patient needs rapid resolution of pain. To this end, intranasal fentanyl spray appeared having a particular importance in clinical practice. Accepted definitions of BTcP should be investigated in future studies to determine the optimal management of this highly heterogeneous pain condition.