Tumor Budding and T1 Substaging in Urothelial Bladder Cancer

Assessment of Tumor Budding and T1 Substaging as Histopathological Predictors of Outcome in Urothelial Bladder Carcinoma

Bladder cancer is a significant global and local health concern, and predicting how aggressive a patient's tumor will behave is critical for guiding treatment. This observational study aims to evaluate two specific microscopic features of urothelial bladder carcinoma to see if they can reliably predict patient outcomes: the depth of early tumor invasion (T1 substaging) and the presence of small clusters of cancer cells at the tumor's edge (Tumor Budding).

Researchers will retrospectively analyze tissue samples (paraffin blocks) from at least 100 patients who were diagnosed with urothelial bladder carcinoma and underwent transurethral resection (TUR) at the South Egypt Cancer Institute between 2018 and 2024.

The tissue samples will be analyzed in two main ways:

• Early-stage tumors (pT1 cases): Researchers will carefully measure the exact depth the tumor has invaded the bladder lining using anatomical and micrometric sub-classification systems.
• More advanced tumors (pT2 cases): Researchers will examine the invasive edge of the tumors under a microscope to count "tumor buds" (single cells or small clusters of cells).

By comparing these detailed microscopic measurements with the patients' historical medical records, the study hopes to determine if T1 substaging and Tumor Budding are strong predictors of disease recurrence, disease progression, and overall patient survival.

Bladder carcinoma remains a major global oncological burden, exerting a substantial impact on patient morbidity and mortality. In Egypt, it constitutes a significant public health concern with distinctive epidemiological characteristics. While squamous cell carcinoma historically predominated, a substantial shift has occurred over recent decades, and urothelial carcinoma has emerged as the dominant subtype, accounting for approximately 75-80% of cases.

Pathological assessment traditionally focuses on histological grade and invasion depth. The precise assessment of invasion depth is critical, particularly in T1 non-muscle-invasive urothelial carcinoma, where the tumor invades the lamina propria. Multiple sub-classification systems exist for T1 tumors, including anatomical approaches relative to the muscularis mucosae and semiquantitative micrometric methods, yet no single method has been adopted universally. Furthermore, in muscle-invasive disease, the morphology of the invasive front provides crucial biological insights. Tumor budding, defined as single isolated cancer cells or small clusters of fewer than five cells at the invasive front, is recognized as a morphological hallmark of epithelial-mesenchymal transition (EMT) and reflects aggressive tumor potential.

This study evaluates archived hematoxylin and eosin (H&E)-stained slides from patients who underwent transurethral resection (TUR) for urothelial carcinoma between 2018 and 2024. Histological subtypes will be confirmed according to the 2022 World Health Organization (WHO) classification, and tumor grade and stage will be determined using the American Joint Committee on Cancer (AJCC) 8th edition. Additional pathological parameters assessed will include tumor size, multifocality, coagulative tumor necrosis, lympho-vascular invasion (LVI), and perineural invasion (PNI).

The histopathological procedures are divided into two primary evaluations:

• pT1 Substaging: Confirmed pT1 cases will undergo rigorous histopathological substaging. Anatomical substaging (T1a/b/c) will identify the invasion level relative to the muscularis mucosae. Micrometric assessment will utilize a 0.1 mm threshold for semi-quantitative subtyping, alongside the Rete Oncologica Lombarda (ROL) system, which uses a 1.0 mm threshold to define low-risk and high-risk progression groups.
• Tumor Budding Assessment: Confirmed pT2 cases will be evaluated for tumor budding at the invasive front using the "Hotspot" method to count buds in one high-power field. Cases will be stratified into three grades: Low Budding (BD1: 0-4 buds), Intermediate Budding (BD2: 5-9 buds), and High Budding (BD3: ≥ 10 buds).

Inclusion Criteria:

• Patients with a urinary bladder mass, diagnosed by TUR biopsy as urothelial carcinoma.
• Patients with full clinical data and complete medical reports.

Exclusion Criteria:

• Cases with non-urothelial histological subtypes (e.g., pure squamous cell carcinoma).
• Patients who received neoadjuvant chemotherapy or radiotherapy.
• Cases with missing or inaccessible clinical follow-up data.
• History of prior or concurrent malignancy.