[Malignant lymphomas in children and adolescents. Practical knowledge for diagnosis].

Malignant lymphomas are very rare in childhood. Therefore in Germany and Europe-wide the diagnosis and treatment of these diseases and research into them are carried out in multicenter-study groups and registries that provide central clinical consulting as well as histopathological, genetic, and molecular diagnoses. Despite these central structures, the diagnosis of these aggressive lymphomas is usually made initially outside these specialized centers. Therefore, in clinical situations that are often quite critical, every pathologist may be required to make the initial diagnosis and decide on the initial therapy regimen. Specific features related to the incidence, biology, and clinical presentation of pediatric lymphomas strongly influence the diagnostic workup and require a different diagnostic procedure from that employed in adults. In this paper, we will try to provide the most important information required for a tissue-saving initial diagnosis of the most common pediatric lymphomas. The proposed procedures allow reliable differentiation into the main lymphoma categories and, thus, provide the necessary information for the first therapeutic regimens, although the final subtyping will remain the responsibility of specialists. The most relevant histopathological features, appropriate immunohistochemical stains, and diagnostic pitfalls are demonstrated. As examples of the most common entities, special attention is paid to Burkitt lymphoma, diffuse large B-cell lymphoma, precursor T- and B-cell lymphoma, and anaplastic large-cell lymphoma.