[Histiocytoses: General classification and molecular criteria]

Area of Science:

• Hematology
• Oncology
• Pathology

Background:

• Histiocytoses are a diverse group of rare disorders characterized by the abnormal accumulation of histiocytes.
• These conditions can be inherited or sporadic, stemming from material buildup in macrophages or macrophage activation.
• Recent research indicates that some histiocytoses, like Langerhans cell histiocytosis and Erdheim-Chester disease, are clonal myeloid proliferations, not merely inflammatory or idiopathic.

Purpose of the Study:

• To provide a comprehensive classification of histiocytoses.
• To outline the diagnostic criteria for idiopathic histiocytoses.
• To detail the molecular criteria for histiocytic neoplasms.

Main Methods:

• Literature review of histiocytosis classifications.
• Analysis of diagnostic criteria for idiopathic histiocytoses.
• Review of molecular findings in histiocytic neoplasms.

Main Results:

• Histiocytoses are reclassified based on new understanding of their origins.
• Diagnostic criteria are refined to distinguish between reactive and neoplastic processes.
• Molecular markers are crucial for identifying clonal myeloid proliferations.

Conclusions:

• A revised classification framework for histiocytoses is proposed.
• Accurate diagnosis relies on integrating histological, clinical, and molecular data.
• Understanding the clonal nature of certain histiocytoses advances therapeutic strategies.