The prognostic value of the morhological types of ALK-positive anaplastic large cell lymphoma in children

The aim of our study is to evaluate the prognostic value of the morphological types of ALK-positive anaplastic large cell lymphoma (ALK+ ALCL) in children. We performed a retrospective analysis of data on 81 cases of pediatric ALK+ ALCL which had been diagnosed in 2011–2022. All patients and/or their legal representatives signed voluntary informed consent for participation in the study, as well as for biological material testing. The analysis of medical records was carried out in accordance with the internal rules of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology of Ministry of Healthсare of the Russian Federation, developed and approved by the Independent Ethics Committee of the Center. The patients received treatment according to the standard protocol. We assessed overall (OS) and event-free (EFS) survival depending on the morphological type of the tumor. The median follow-up was 55.6 months. Three-year and 5-year OS rates were 81.9% and 79.8%, respectively. Three-year and 5-year EFS rates were 59.6% and 56.0%, respectively. There were no statistically significant differences in OS and EFS between the common and non-common morphological types of ALK+ ALCL. Better survival rates were observed in the patients with a lymphohistiocytic variant. We found statistically significant differences in OS (p = 0.031) and EFS (p = 0.002) between the cases with a small cell component and without it. The results suggest that ALK+ ALCL with small cell morphology has a more aggressive course in children. Validation in larger patient cohorts and further study of the biology of different morphological types are needed to develop stratified treatment approaches.