Urothelial carcinoma in situ: diagnostic update

Next-generation sequencing has diagnostic utility in challenging small/flat urothelial lesions

Small/flat urothelial lesions are challenging and currently available ancillary immunohistochemistry testing often cannot reliably distinguish between reactive lesions and urothelial carcinoma (UCa). UCa has a characteristic molecular profile, but small/flat urothelial lesions are typically considered too small to perform next generation sequencing (NGS). Herein, we present our institution's experience with utilizing comprehensive DNA-based NGS to evaluate small/flat urothelial lesions (n = 13 cases). NGS was ordered on 7/13 small/flat urothelial lesions initially diagnosed as urothelial atypia, ordered by the pathologist to aid in further diagnosis; the remaining 6/13 cases were diagnosed as urothelial carcinoma in situ (uCIS), ordered by a treating oncologist. The test was considered as adding value if it yielded pathogenic or likely pathogenic alterations previously associated with urothelial carcinoma in the literature. Macroscopic dissection was determined necessary in all cases and obtained either by scraping (7), punch biopsy (5) or scooping (1) of paraffin tissue blocks. In 4/13 cases, tumor content was considered low (<25%); in 2/13 cases, DNA quantity yield was considered below optimal (<250 ng); all cases met required DNA quantity for testing (>50 ng). Mean target coverage ranged: 498 to 985 (optimal >500 reads). NGS testing identified mutations compatible with urothelial carcinoma in all 7 cases initially diagnosed as atypical; and in one case, the tumor recurred as a lung metastasis. All 6 uCIS had NGS testing results concordant with UCa. In conclusion, despite small sample quantity with low tumor content and DNA concentration yield, NGS testing with appropriate methodology can be considered in the setting of small/flat urothelial lesions to aid in diagnosis or per oncologist request and yield interpretable results.

Recent Advances in Genitourinary Tumors: Updates From the 5th Edition of the World Health Organization Blue Book Series

CONTEXT.—

Urinary and Male Genital Tumours is the 8th volume of the World Health Organization Classification of Tumours series, 5th edition. Released in hard copy in September 2022, it presents an update to the classification of male genital and urinary tumors in the molecular age. Building upon previous volumes in this series, significant effort has been made to harmonize terminology across organ systems for biologically similar tumors (eg, neuroendocrine tumors). Genomic terminology has been standardized and genetic syndromes covered more comprehensively. This review presents a concise summary of this volume, highlighting new entities, notable modifications relative to the 4th edition, and elements of relevance to routine clinical practice.

OBJECTIVE.—

To provide a comprehensive update on the World Health Organization classification of urinary and male genital tumors, highlighting updated diagnostic criteria and terminology.

DATA SOURCES.—

The 4th and 5th editions of the World Health Organization Classification of Tumours: Urinary and Male Genital Tumours.

CONCLUSIONS.—

The World Health Organization has made several changes in the 5th edition of the update on urinary and male genital tumors that pathologists need to be aware of for up-to-date clinical practice.

Zosteriform cutaneous metastases from urothelial carcinoma: Report of a rare case and literature review

Zosteriform cutaneous metastases from urothelial carcinoma are rare. Here, we report a 50-year-old male with urothelial carcinoma who presented with multiple tender, erythematous papulonodules in an L1-L3 distribution approximately 6 years after primary tumor diagnosis. He had no history of prior herpes zoster infection. Histopathology showed lobules and small nests of atypical epithelioid cells positive for GATA3, CK20, CK7, and p40 throughout the dermis and within lymphatic vessels highlighted by D2-40, consistent with cutaneous metastases from urothelial carcinoma. No perineural invasion or viral cytopathic change was present. The patient died approximately 8 months after diagnosis of cutaneous metastases. Since its first report in 1986, there have been only six cases of zosteriform cutaneous metastases from urothelial carcinoma. We review the prior literature including hypotheses of the pathogenesis of zosteriform cutaneous metastases, which remain incompletely understood.

Recent Advances in the Classification of Bladder Cancer - Updates from the 5th Edition of the World Health Organization Classification of the Urinary and Male Genital Tumors

BACKGROUND

The World Health Organization Classification (WHO) of Urinary and Male Genital Tumors has recently been updated to its 5th edition. The new edition presents a comprehensive approach to the classification of urinary and male genital tumors with an incorporation of morphologic, clinical, and genomic data.

OBJECTIVE

This review aims to update the new classification of bladder cancer in the 5th edition and to highlight important changes in nomenclatures, diagnostic criteria, and molecular characterization, as compared to the 4th edition.

METHODS

The pathologic classification of bladder cancer in the 5th edition of WHO Classification of Urinary and Male Genital Tumours was compared to that in the 4th edition. PubMed was searched using key words, including bladder cancer, WHO 1973, WHO 1998, WHO 2004, WHO 2016, histology, pathology, genomics, and molecular classification in the time frame from 1973 to August of 2022. Other relevant papers were also consulted, resulting in the selection of 81 papers as references.

RESULTS

The binary grading of papillary urothelial carcinoma (UC) is practical, but it may be oversimplified and contribute to "grade migration" in recent years. An arbitrary cutoff (5%) has been proposed for bladder cancers with mixed grades. The diagnosis of papillary urothelial neoplasm with low malignant potential has been dramatically reduced in recent years because of overlapping morphology and treatment with low-grade papillary UC. An inverted growth pattern should be distinguished from true (or destructive) stromal invasion in papillary UC. Several methods have been proposed for pT1 tumor substaging, but it is often challenging to substage pT1 tumors in small biopsy specimens. Bladder UC shows a high tendency for divergent differentiation, leading to several distinct histologic subtypes associated with an aggressive clinical behavior. Molecular classification based on the genomic analysis may be a useful tool in the stratification of patients for optimal treatment.

CONCLUSIONS

The 5th edition of WHO Classification of Urinary and Male Genital Tumours has made several significant changes in the classification of bladder cancer. It is important to be aware of these changes and to incorporate them into routine clinical practice.

Urothelial carcinoma in situ with "overriding" features can evade detection by mimicking umbrella cells

Urothelial carcinoma in situ (uCIS) is typically recognized by overtly malignant cells with characteristic nuclear features; multiple histologic patterns have been described. A rare "overriding" pattern, in which uCIS tumor cells extend on top of normal urothelium, has previously been mentioned in the literature, but not well-described. Herein, we report three cases of uCIS with "overriding" features. Detailed morphologic evaluation revealed somewhat subtle cytologic atypia: variably enlarged hyperchromatic nuclei, scattered mitotic figures but with abundant cytoplasm and limited to superficial urothelium. Immunohistochemical (IHC) analysis showed a distinctive diffuse positive aberrant p53 pattern, limited to the atypical surface urothelial cells; these cells were also CK20+, CD44-, and Ki67 increased. In two cases, there was a history of urothelial carcinoma and adjacent conventional uCIS. In the third case, the "overriding" pattern was the first presentation of urothelial carcinoma; therefore next generation sequencing molecular testing was also performed, revealing pathogenic mutations in TERTp, TP53, and CDKN1a to further support neoplasia. Notably, the "overriding" pattern mimicked umbrella cells, which normally line surface urothelium, can have abundant cytoplasm, more variation in nuclear and cell size and shape, and show CK20+ IHC. We therefore also evaluated umbrella cell IHC patterns in adjacent benign/reactive urothelium, which showed CK20+, CD44-, p53 wild-type and very low Ki67 (3/3). We also reviewed 32 cases of normal/reactive urothelium: all showed p53 wild-type IHC in the umbrella cell layer (32/32). In conclusion, caution is warranted to avoid overdiagnosis of usual umbrella cells as CIS; however, "overriding" uCIS should be recognized, may have morphologic features that fall short of the diagnostic threshold of conventional CIS, and requires further study.

Scoring Systems for Immunohistochemistry in Urothelial Carcinoma

Immunohistochemistry is widely used in diagnostic and scientific analysis of urothelial carcinoma. Objective interpretation of staining results is mandatory for accuracy and comparability in diagnostic and therapeutic patient care as well as research.Herein we summarize and explain standardized microscopic evaluation and scoring approaches for immunohistochemical stainings. We focus on commonly used and generally feasible approaches for different cellular compartments and comment on their utility in diagnostics and research practice.

Flat intraurothelial lesions of the urinary bladder-do hyperplasia, dysplasia, and atypia of unknown significance need to exist as diagnostic entities? and how to handle in routine clinical practice

Classification of the putative flat preneoplastic and neoplastic lesions of the urothelium with features subthreshold for urothelial carcinoma in situ remains a challenging, indeed, vexing problem in diagnostic surgical pathology. This area, subtending lesions including flat urothelial hyperplasia, urothelial dysplasia, and atypia of unknown significance, has struggled under evolving classifications, changing criteria, and limited clinical actionability, all confounded by the recognized lack of diagnostic reproducibility. Herein, we review the state of the literature around these lesions, reviewing contemporary criteria and definitions, assessing the arguments in favor and against of retaining hyperplasia, dysplasia, and atypia of unknown significance as diagnostic entities. We clarify the intent of the original definitions for dysplasia as a lesion felt to be clearly neoplastic but with morphologic features that fall short of the threshold of urothelial carcinoma in situ. While several pathologists, including some experts in the field, conflate the term dysplasia with urothelial atypia of unknown significance, the latter is defined as a descriptive diagnosis term to express diagnostic uncertainty of a lesion of whether it is clearly reactive or neoplastic. Both molecular studies and clinical needs are considered, as we outline our approach on diagnosing each of these lesions in clinical practice. Recommendations are made to guide consistency and interoperability in future scholarship, and the place of these lesions in context of evolving trends in the field is considered.