: The classification reaffirms the 9-pathway model for melanoma, which classifies lesions based on sun exposure (UV damage), anatomical site (e.g., acral, mucosal), and specific molecular drivers.
: "Primary cutaneous NUT (Nuclear protein in testis) carcinoma" is included as a new provisional entity. 4. Adnexal & Soft Tissue Tumours WHO Classification of Skin Tumours
: Updates focus on high-risk subtypes. Sarcomatoid differentiation is now the primary acknowledged uncommon subtype of Squamous Cell Carcinoma (SCC). : The classification reaffirms the 9-pathway model for
: This term is now used for "intermediate" lesions that exhibit borderline biological behavior but have specific molecular signatures (e.g., BAP1 inactivation or WNT pathway alterations). Adnexal & Soft Tissue Tumours : Updates focus
: Entities are now generally listed in order from benign to malignant within each section to better reflect their neoplastic progression and clinical aggressiveness.
The (5th Edition, 2025) is the authoritative global standard for diagnosing and categorizing cutaneous neoplasms. Also known as the "Blue Books," this edition shifts toward a more integrated, multidisciplinary approach that combines traditional histopathology with advanced molecular genetics and immunohistochemistry. Key Structural & Conceptual Changes