Clear Cell Urothelial Carcinoma

Area of Science:

• Uropathology
• Oncology
• Cancer Biology

Background:

• Clear cell urothelial carcinoma (CCUC) is a rare variant of urothelial carcinoma (UC).
• Its clinical significance and distinct pathological features are not well understood.
• Distinguishing CCUC from other urothelial neoplasms is crucial for accurate diagnosis and prognosis.

Purpose of the Study:

• To characterize the histopathological features of CCUC.
• To evaluate the clinical outcomes associated with CCUC.
• To investigate the immunohistochemical profile of CCUC and compare it with non-CCUC.

Main Methods:

• Retrospective review of 872 urothelial carcinoma (UC) cases over 5 years.
• Identification and detailed histopathological analysis of 10 clear cell urothelial carcinoma (CCUC) cases.
• Immunohistochemical analysis using markers CK7, CK20, CK5, CD44, and PAX8.
• Literature review for additional CCUC case reports and series.

Main Results:

• Ten CCUC cases were identified, with clear cell change comprising 30-90% of the invasive tumor component.
• Focal clear cell change (<5% of cells) was observed in over 50% of non-CCUC cases.
• CCUC cases frequently showed advanced stage (8/10) and poor outcomes (6/10 recurrence/death).
• Immunohistochemistry revealed CCUC positivity for CK5/CD44 (9/10), CK20 (5/10), PAX8 (6/10), and CK7 (10/10).

Conclusions:

• CCUC is defined by extensive clear cell change (>30% of tumor cells).
• This variant is associated with aggressive clinical behavior, including rapid progression, muscle invasion, and metastasis.
• Immunohistochemical markers like CK5/CD44 may indicate basal cell features, while PAX8 suggests potential mesonephric origin.