Anaplastic large cell lymphoma (ALCL) is a rare type of non-Hodgkin lymphoma characterized by the presence of large cells with abundant cytoplasm and pleomorphic nuclei, often expressing the CD30 antigen. It can be divided into two main types: systemic ALCL, which is more aggressive and can affect lymph nodes and extranodal sites, and primary cutaneous ALCL, which is less aggressive and primarily affects the skin.