Renal Tumors: Histopathology and Grading

Renal tumors encompass a spectrum of benign and malignant neoplasms that originate in the kidneys. Histopathological analysis plays a critical role in diagnosing, classifying, and grading these tumors.

Histopathology of Renal Tumors

Histopathology involves microscopic examination of tissue samples to determine cellular morphology and tumor architecture.

Common Renal Tumors

• Renal Cell Carcinoma (RCC): The most prevalent malignant tumor, subtypes include clear cell RCC, papillary RCC, and chromophobe RCC.
• Wilms Tumor: A pediatric nephroblastoma with embryonal origin.
• Oncocytoma: A benign epithelial tumor characterized by abundant eosinophilic cytoplasm.

Grading of Renal Tumors

Tumor grading assesses the differentiation of cancer cells, influencing prognosis and treatment approaches.

Fuhrman Nuclear Grading

The traditional grading system for RCC based on nuclear features:

• Grade 1: Small, uniform nuclei with inconspicuous nucleoli.
• Grade 2: Larger nuclei with visible nucleoli.
• Grade 3: Prominent nucleoli, increased nuclear pleomorphism.
• Grade 4: Marked nuclear atypia with giant cells and irregular mitoses.

WHO/ISUP Grading

A more recent classification focused on clear cell and papillary RCC, emphasizing nucleolar prominence.

Diagnostic and Prognostic Significance

Histopathological grading informs prognosis, guiding surgical and therapeutic interventions. Higher grades correlate with aggressive behavior and poor outcomes.