[Tumors of dendritic and other accessory cells of lymph nodes]

Besides the obviously much more common lymphomas, neoplasms of dendritic and other so-called accessory cells can also primarily originate in lymph nodes. These include histiocytic sarcomas, follicular dendritic cell sarcomas, interdigitating dendritic cell sarcomas, fibroblastic reticulum cell tumors/cytokeratin-positive interstitial cell neoplasms and neoplasms of indeterminate dendritic cells. A feature common to all of these tumors is the very difficult differential diagnosis, not least because of their rarity; however, a careful analysis will allow discrimination from other sarcomas, sarcomatoid carcinomas, lymphomas and melanomas and lead to the correct classification of the respective lesions. From the pathogenetic view point it is interesting that there is an increased association of these tumors with lymphomas and leukemias. Moreover, many cases demonstrate shared clonal antigen receptor rearrangements and/or recurrent genetic aberrations in both histologically different tumor components. This suggests a common precursor cell or at least a common derivation.