Histiocytic neoplasm

Histiocytic neoplasms are a rare and diverse group of tumors that develop from a class of immune cells called histiocytes, which include macrophages, dendritic cells, and monocytes. These conditions include several distinct disorders, such as Langerhans cell histiocytosis, Erdheim-Chester disease, juvenile xanthogranuloma, Rosai-Dorfman disease, and histiocytic sarcoma. Although all of these diseases involve the abnormal growth of histiocytes, they can behave very differently. Some may cause mild symptoms that self-resolve, while others can develop into aggressive life-threatening malignancies.
Many histiocytic neoplasms have been found to share recurrent genetic alterations, particularly involving the MAPK signaling pathway. These discoveries have established that many of these disorders represent clonal neoplastic diseases rather than purely reactive conditions. This molecular insight has contributed to more precise classification of histiocytic neoplasms and has facilitated the development of targeted therapies that have improved clinical outcomes in some patients.