Can We Identify Nephrogenic Adenoma in Urine Cytology Specimens? A Study Evaluating Previously Described Cytomorphologic Features in Correlation With PAX8 Immunohistochemical Staining Results

Urinary Tract Cytopathology: Current and Future Impact on Patient Care

Urine cytology is a non-invasive, cost-efficient, and sensitive test to detect high-grade urothelial carcinoma. The Paris System (TPS) for Reporting Urinary Cytology is an evidence-based system that uses the risk of malignancy to guide patient management. Since its inception, TPS has standardized urine cytology reports, facilitating communication among pathologists and between pathologists and clinicians. It is imperative to correlate the urine cytology findings with the concurrent tissue sample to avoid false-negative and false-positive results when possible. Several ancillary tests and artificial intelligence algorithms are being developed to increase the accuracy of urine cytology interpretation.

Pitfalls in Urinary Tract Cytopathology

BACKGROUND

Urine cytopathology is a cost-effective method to diagnose and follow patients with high-grade urothelial carcinoma (UC). However, some benign, reactive, and metaplastic changes may mimic UC and pose a diagnostic challenge for cytopathologists.

SUMMARY

Our comprehensive review focuses on summarizing common pitfalls encountered in urine cytopathology, based on the 2nd edition of The Paris System (TPS) for reporting urinary tract cytopathology and other recent published literature. These pitfalls include urothelial tissue fragments, degenerative changes, treatment effects, viral cytopathic changes, iatrogenic and metaplastic changes. Our aim was to provide a clear understanding of these mimics in order to avoid diagnostic errors.

KEY MESSAGE

It is crucial for cytopathologists to recognize benign, reactive, or metaplastic lesions that sometimes resemble UC. An awareness of these cytological changes is essential to make an accurate diagnosis.

10-Year observation of a rare presentation of pure fibromyxoid nephrogenic adenoma in the renal pelvis

Nephrogenic adenoma (NA) is an unusual benign epithelial tumor in the genitourinary tract. Here we report a fibromyxoid nephrogenic adenoma in a 37-year-old female presenting with over 10-year slow-growing renal pelvic mass that was diagnosed with bland spindle cell lesion in multiple previous biopsies. This is the first reported case of pure fibromyxoid NA in renal pelvis with close comparison and correlation of biopsy and resection findings over a 10-year span. This will enhance awareness of pathologists to consider this unusual entity when examining spindle cell lesions in this setting, and prevent misdiagnosis and overtreatment of a typically benign process.

Urine Cytology Findings in Cases of Pseudocarcinomatous Urothelial Hyperplasia of the Bladder Often Represent a Diagnostic Challenge

CONTEXT.—

Pseudocarcinomatous urothelial hyperplasia (PCUH) architecturally and cytologically mimics cancer. The urine cytology features of PCUH have not been described.

OBJECTIVE.—

To describe PCUH features in urine cytology.

DESIGN.—

We reviewed urine cytology cases with concurrent PCUH tissue specimens from 5 academic institutions and classified them by using The Paris System criteria.

RESULTS.—

Thirty-nine patients included 31 men and 8 women with a mean age of 67 years (range, 39-87 years). All patients had prior pelvic irradiation, and most presented with hematuria (n = 27). The specimens included voided urine (n = 16); bladder washing (n = 11); and urine, not otherwise specified (n = 12). The specimen preparation included cytospin (n = 29) and ThinPrep (n = 10). Original interpretations were negative for high-grade urothelial carcinoma (n = 28), atypical urothelial cells (AUCs; n = 10), and high-grade urothelial carcinoma (HGUC; n = 1). Twenty-five urine specimens (64%) had findings of PCUH. These specimens were moderately cellular and composed of sheets, cohesive groups, or isolated urothelial cells. Nucleoli were present in 23 cases. The nuclear membrane was smooth to irregular (n = 9), smooth (n = 8), and irregular (n = 8). The chromatin was glassy (n = 8), vesicular (n = 7), hyperchromatic (n = 7), and vesicular to finely granular (n = 3). The cytoplasm varied from dense squamoid, to finely vacuolated, to vacuolated. Nucleomegaly was observed in all 25 specimens, and nuclear-cytoplasmic ratio greater than 0.5 was seen in 11 of 25 cases (44%). The background contained acute inflammation (n = 14), was clean (n = 9), and contained red blood cells (n = 2). All cases originally interpreted as AUCs and HGUC had PCUH features.

CONCLUSIONS.—

PCUH urine features can overlap with AUCs, HGUC, and other nonurothelial malignancies. In our cohort, 44% (11 of 25) of urine specimens with PCUH changes were initially misclassified. Recognition of cytologic features of PCUH is important to avoid overcalling reactive changes.

Common and uncommon features of nephrogenic adenoma revisited

Nephrogenic adenoma is a common diagnosis in urological pathology that may be challenging for general pathologists. Due to its polymorphic appearance under the microscope, some cases can be misdiagnosed as malignancy and then unnecessarily overtreated. Aside from the typical tubules, cysts and papillae, nephrogenic adenoma may display a broad spectrum of histologic appearances and locations, some of them atypical or unexpected. These unusual and concerning features will have special consideration in this description. The goal of the review is to increase awareness of general pathologists of the varied histology of nephrogenic adenoma.