What's new in the WHO 2022 classification of kidney tumours?

Area of Science:

• Uropathology
• Oncology
• Genitourinary Pathology

Background:

• The World Health Organization (WHO) classification is crucial for standardizing tumour diagnosis.
• Previous classifications required updates to incorporate advances in renal tumour understanding.
• The 5th edition (2022) addresses morphologic, immunohistochemical, and molecular characteristics of renal tumours.

Purpose of the Study:

• To review significant changes and diagnostic updates in the WHO 2022 classification of kidney tumours.
• To highlight newly defined entities and revised tumour groupings.
• To emphasize the integration of molecular data in renal tumour classification.

Main Methods:

• Review of the World Health Organization (WHO) 2022 classification of urinary and male genital tumours.
• Analysis of diagnostic updates, including new tumour entities and broader categories.
• Focus on morphologic, immunohistochemical, and molecular features.

Main Results:

• Renal tumours are now grouped into broader categories: clear cell, papillary, oncocytic and chromophobe, collecting duct, other renal tumours, and molecularly defined renal carcinomas.
• Novel entities include eosinophilic solid and cystic renal cell carcinoma (ESC RCC), ALK-rearranged RCC, and ELOC-mutated RCC.
• Molecularly defined renal carcinomas highlight genotype-phenotype relationships, often diagnosed using IHC surrogate markers.

Conclusions:

• The WHO 2022 classification represents a significant advancement in understanding and diagnosing renal tumours.
• New categories and entities, particularly molecularly defined ones, enhance diagnostic precision.
• Phenotypic and immunohistochemical correlation remains essential for final diagnosis, especially for genetically defined entities.