Anaplastic large cell lymphoma (ALCL) refers to a group of non-Hodgkin lymphomas in which aberrant T cells proliferate uncontrollably. Considered as a single entity, ALCL is the most common type of peripheral lymphoma and represents ~10% of all peripheral lymphomas in children. The incidence of ALCL is estimated to be 0.25 cases per 100,000 people in the United States of America. There are four distinct types of anaplastic large cell lymphomas that on microscopic examination share certain key histopathological features and tumor marker proteins. However, the four types have very different clinical presentations, gene abnormalities, prognoses, and/or treatments.ALCL is defined based on microscopic histopathological examination of involved tissues which shows the presence of at least some ALCL-defining pleomorphic cells. These "hallmark" cells have abnormal kidney-shaped or horseshoe-shaped nuclei, prominent Golgi, and express the CD30 tumor marker protein on their surface membranes. In 2016, the World Health Organization (WHO) separated ALCL into four types: ALK-positive ALCL (also termed ALK+ ALCL), ALK-negative ALCL (ALK− ALCL), primary cutaneous ALCL (pcALCL), and breast implant-associated ALCL (BIA-ALCL). WHO defined BIA-ALCL as an ALCL type provisionally, i.e. subject to redefinition if future studies should support such a change.ALK-positive and ALK-negative ALCL are aggressive systemic lymphomas. They are differentiated based on their expression of an abnormal ALK protein made by a somatic recombination in the ALK gene. ALK, i.e. anaplastic lymphoma kinase, is a protein product of the ALK gene located on chromosome 2.
These as well as individuals who relapse after front-line therapy need further treatment. In one study of 65 patients with pcALCL, 95% treated with surgical excision achieved complete remission but 41% of them relapsed within 22 months while 64% of patients treated with surgery plus radiotherapy developed recurrent disease within 55 months. In another study of 135 patients with this disease, 39% had relapses limited to the skin, 15% developed extracutaneous disease, and 9% ultimately died from pcALCL. Individuals with refractory, recurrent, and/or extensive disease have been treated more aggressively. In various studies, 10 of 13 such patients responded within 4 weeks to treatment with the chemotherapeutic agent, methotrexate; 10 of 16 patients obtained complete remissions of their skin lesions when treated with the anti-CD30 monoclonal antibody, brentuximab verdotin, and 48 of 53 patients treated with the aggressive chemotherapeutic CHOP regimen had complete responses. However, most of these patients developed recurrent disease within four months. As currently recommended, brentuximab vedotin is use initially to treat widespread systemic disease; a single chemotherapeutic drug rather than aggressive combination chemotherapy with CHOP or similar regimens is used to treat patients not responding to brentuximab verdotin; aggressive chemotherapy regimens are used to treat widespread nodal and/of visceral disease and disease which failed on other regiments; and, although there is little data supporting this, employ allogeneic bone marrow transplantation for patients with multiple relapses that have progressed on systemic therapy. Recurrences, regardless of treatment type, are common. pcALCL has an estimated five-year failure-free survival rate of 55 percent.