Urinary Tract Cytology

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Urinary Specimens & Normal Cells - What's In Your Wee?

  • Specimen Types:
    • Voided (midstream clean-catch): Most common.
    • Catheterized: Avoids vulvovaginal contamination.
    • Bladder Washings/Lavage: ↑ cellularity, for suspected lesions.
    • Ileal Conduit: Post-cystectomy.
    • Ureteric/Renal Pelvic Brushings: Upper tract evaluation.
  • Processing & Preservation:
    • Fresh: Examine within 1-2 hrs.
    • Refrigerate (4°C): Up to 24 hrs.
    • Fixatives: 50% Ethanol, Saccomanno (Carbowax).
  • Normal Cellular Elements:
    • Urothelial (Transitional): Superficial (umbrella), intermediate, deep (basal).
    • Squamous: Common (esp. females); usually contaminants.
    • RBCs: <5/HPF.
    • WBCs: <5/HPF (neutrophils).
    • Casts: Occasional hyaline.
    • Crystals, mucus, spermatozoa. Normal urothelial and squamous cells in urine

⭐ Deep urothelial cells naturally show a higher N/C ratio than superficial cells; misinterpreting this as atypia is a common pitfall.

Benign & Reactive Atypia - Not Always Bad News

  • Non-neoplastic cellular changes that can mimic malignancy; crucial for differential diagnosis.
  • Common Causes:
    • Inflammation (UTI): Neutrophils, bacteria, reactive urothelial cells.
    • Urolithiasis (stones): Mechanical irritation, cell clusters, mild atypia.
    • Instrumentation (catheter, cystoscopy): Sheets or clusters of reactive cells.
    • Therapy-induced changes:
      • Radiation: Cytomegaly, nucleomegaly, bizarre cell shapes, smudged chromatin, but often maintained N/C ratio.
      • Chemotherapy (e.g., Cyclophosphamide, Thiotepa): Similar to radiation; multinucleation common.
  • Key Cytologic Features:
    • Mild nuclear enlargement, smooth nuclear membranes.
    • Finely granular, evenly distributed chromatin (or smudged/degenerated).
    • Prominent, centrally located nucleoli (if reactive).
    • Inflammatory background, cytoplasmic vacuolization. Decoy cell in urinary tract cytology

⭐ Polyomavirus (BK virus) infection characteristically produces "Decoy cells": urothelial cells with large, homogenous, basophilic or amphophilic ground-glass intranuclear inclusions, which can be mistaken for High-Grade Urothelial Carcinoma (HGUC), especially in immunocompromised patients like renal transplant recipients.

Urothelial Neoplasia & Paris System - Grading the Grim

The Paris System (TPS) for Reporting Urinary Cytology standardizes diagnosis, enhancing High-Grade Urothelial Carcinoma (HGUC) detection and reducing Atypical Urothelial Cells (AUC) rates.

  • Core Principle: Identify HGUC; other findings are secondary.

  • Key TPS Diagnostic Categories:

    • Non-Diagnostic (ND)
    • Negative for HGUC (NHGUC)
    • Atypical Urothelial Cells (AUC)
    • Suspicious for HGUC (SHGUC)
    • High-Grade Urothelial Carcinoma (HGUC)
    • Low-Grade Urothelial Neoplasm (LGUN)
  • HGUC Cytomorphologic Criteria (Mandatory):

    • Nuclear to Cytoplasmic (N/C) ratio ≥ 0.7
    • Severe hyperchromasia
    • Marked nuclear pleomorphism (size/shape variation)
    • Irregular nuclear contours/notched nuclei
    • Coarsely granular, clumped chromatin

High-Grade Urothelial Carcinoma Cytology Examples

⭐ The Paris System (TPS) aims for high sensitivity for HGUC (>85%) while maintaining specificity, significantly improving interobserver reproducibility for HGUC diagnosis.

Other Malignancies & Ancillary Tests - Beyond Urothelial Scope

  • Non-Urothelial Primaries:
    • Squamous Cell Ca (SCC): Chronic irritation (Schistosoma). Keratin, bizarre cells. Markers: p63, CK5/6.
    • Adenocarcinoma: Glandular, mucin. Primary (e.g., urachal) vs. metastatic (colorectal, prostate). Markers: CK7, CK20, CDX2, PSA.
    • Small Cell Ca: Neuroendocrine. Nuclear molding, scant cytoplasm. Markers: Synaptophysin, Chromogranin.
  • Metastatic Tumors: Most frequent non-urothelial. Common sources: prostate, colorectal, renal (RCC), lung, melanoma, lymphoma.
  • Ancillary Tests (General):
    • Immunocytochemistry (ICC): Key for lineage. Examples above.
    • Molecular: FISH (UroVysion for urothelial Ca, detects aneuploidy of chr 3, 7, 17; 9p21 loss).

⭐ In urine cytology, adenocarcinoma cells from prostate typically show PSA & PSAP positivity.

High‑Yield Points - ⚡ Biggest Takeaways

  • Voided urine is most common; catheterized for upper tract. Papanicolaou stain is standard.
  • Decoy cells (polyomavirus) are key mimics of High-Grade Urothelial Carcinoma (HGUC).
  • HGUC criteria: high N/C ratio, marked pleomorphism, coarse chromatin, irregular nuclear membranes.
  • Low-Grade Urothelial Neoplasms (LGUN) show minimal atypia, making cytology diagnosis challenging.
  • The Paris System (TPS) standardizes reporting, emphasizing HGUC detection.
  • Schistosoma haematobium infection is a risk factor for squamous cell carcinoma.

Practice Questions: Urinary Tract Cytology

Test your understanding with these related questions

A 45-year-old man who works in a textile company visited hospital for routine health check-up. He prepares dyes in the company for the last 18 years. Which of the following investigation would you recommend for this patient?

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Flashcards: Urinary Tract Cytology

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Class II PAP consists of CIN grade _____ and Bethesda grade ASCUS/inflammatory or HPV

TAP TO REVEAL ANSWER

Class II PAP consists of CIN grade _____ and Bethesda grade ASCUS/inflammatory or HPV

inflammatory

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