Recent advances in mastocytosis and neoplasms of probable monocytic/dendritic cell lineage

In recent years, there has been a better appreciation of mast cell and monocyte/macrophage/histiocyte/dendritic cell ontogeny, which has led to reclassification of certain entities within the World Health Organization (WHO) classification of tumours of haematopoietic and lymphoid tissues. Notably, mastocytosis has been reclassified as a chronic myeloproliferative neoplasm, while the former “blastic natural killer cell lymphoma” or “haematodermic neoplasm” is now known as a blastic plasmacytoid dendritic cell neoplasm and classified with the acute leukaemias. This review aims to give a brief overview of the physiological roles and patterns of migration of the corresponding normal cells before discussing the presentation and diagnostic features of mast cell and monocyte/dendritic cell neoplasms. Distinguishing reactive from neoplastic proliferations still poses major challenges and the reasons for this are briefly explained.