Which histiocytosis disorders are classified as M Group (malignant histiocytosis)?

Updated: Sep 16, 2020
  • Author: Cameron K Tebbi, MD; Chief Editor: Vikramjit S Kanwar, MBBS, MBA, MRCP(UK), FAAP  more...
  • Print

The M group includes primary and secondary malignant histiocytosis.

Primary malignant histiocytosis

This is characterized by negative phenotypic analysis for keratins, epithelial membrane antigen (EMA), Melan-A, HMB45, follicular dendritic cell markers, and B- and T-lymphocyte markers, as well as positivity for at least two of the following markers: CD68, CD163, CD4, and lysozyme. Primary malignant histiocytosis is localized to the skin, lymph nodes, digestive system, central nervous system (CNS), or others or is disseminated.

Secondary malignant histiocytosis

This occurs following or in association with conditions such as the following:

  • Follicular lymphoma
  • Lymphocytic leukemia/lymphoma
  • Hairy cell leukemia
  • Acute lymphoblastic leukemia
  • Histiocytosis (Langerhans cell histiocytosis, Rosai-Dorfman disease, others)
  • Other hematologic neoplasias

Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!