Cognitive Radio Network (CRN) plays a critical role in achieving better wireless bandwidth utilization and improving the quality of wireless applications. Multicasting in CRN is a challenging problem due to the dynamic nature of spectrum opportunities available to the secondary users. Researchers have proposed a variety of schemes for efficient multicast in cognitive radio networks, including schemes based on optimization theory, network coding, machine learning, and game theory. The algorithms and techniques for solving the multicast problem effectively were summarized, and a comprehensive survey of protocols was given. Finally, future research directions were identified.