Volume 35, Issue 2 pp. 199-212
REVIEW

Urinary tract cytology showing variant morphology and divergent differentiation

Asma Arshia

Asma Arshia

Department of Pathology and Laboratory Medicine, University of Kentucky College of Medicine, Lexington, Kentucky, USA

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Faisal A. Hassan

Faisal A. Hassan

Department of Pathology and Laboratory Medicine, University of Kentucky College of Medicine, Lexington, Kentucky, USA

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Patrick J. Hensley

Patrick J. Hensley

Markey Cancer Center, Lexington, Kentucky, USA

Department of Urology, University of Kentucky College of Medicine, Lexington, Kentucky, USA

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Derek B. Allison

Corresponding Author

Derek B. Allison

Department of Pathology and Laboratory Medicine, University of Kentucky College of Medicine, Lexington, Kentucky, USA

Markey Cancer Center, Lexington, Kentucky, USA

Department of Urology, University of Kentucky College of Medicine, Lexington, Kentucky, USA

Correspondence

Derek B. Allison, Department of Pathology & Laboratory Medicine, University of Kentucky College of Medicine and Markey Cancer Center, 800 Rose St, MS117, Lexington, KY 40536, USA.

Email: [email protected]

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First published: 02 November 2023
Citations: 1

Abstract

Urothelial carcinoma represents a diverse group of tumours with distinct histologic subtypes, each exhibiting unique cytomorphologic features, architectural growth patterns, and/or well-developed aberrant differentiation. In fact, there are more than 13 subtypes of urothelial carcinoma recognized in the 2022 WHO classification of tumours in the urinary tract. The identification of these subtypes is crucial for an accurate diagnosis of urothelial carcinoma, and many have important clinical implications. Variant/divergent features may coexist with conventional high-grade urothelial carcinoma (HGUC) or present with 100% variant morphology. In urinary tract cytology (UTC), urothelial carcinoma can display divergent differentiation, such as squamous, glandular, or small cell carcinoma differentiation. The use of cell block preparations and immunohistochemistry with available residual urine can enhance diagnostic accuracy. On the other hand, identifying urothelial carcinoma variants, including nested, micropapillary, and plasmacytoid subtypes, poses significant challenges in UTC. Many cases of these variants are only detected retrospectively after variant histology has been established from resection specimens. Moreover, some variants exhibit features inconsistent with the diagnostic criteria for HGUC according to the Paris System for Reporting Urinary Tract Cytology. Nevertheless, the rarity of pure variant morphology and the occurrence of some false negatives for these variant cases are essential to maintain the specificity of UTC overall. This review covers the histology, cytomorphology, and important clinical aspects observed in urothelial carcinoma exhibiting divergent differentiation and various urothelial carcinoma variants detected in UTC.

Graphical Abstract

Urinary tract cytology plays a vital role in diagnosing and managing urothelial carcinoma, particularly in identifying conventional HGUC. However, recognizing variant features in cytology specimens can be challenging, and caution should be exercised.

CONFLICT OF INTEREST STATEMENT

The authors have no conflicts of interest to disclose.

DATA AVAILABILITY STATEMENT

Not applicable; this is a review article.

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