May is Bladder Cancer Awareness Month, one of the most common urologic malignancies in the world. In recent decades, the diagnosis and follow-up of this disease have experienced a real revolution thanks to the evolution of urinary cytology: from the classic conventional smear to modern liquid cytology and the introduction of standardized systems such as The Paris System.

This evolution has not only been a technical laboratory improvement, but has had a concrete impact on patients' lives: more accurate diagnoses, greater standardization, reduction of unnecessary invasive tests, and more targeted follow-ups.

The history of modern cytology is closely linked to the studies of George Papanicolaou, who in the 1940s demonstrated the diagnostic importance of exfoliated cells in biological fluids. On this basis, in the 1950s urinary cytology began to be used in the diagnosis of urothelial carcinoma, particularly high-grade lesions.

The conventional method included:

- Urine collection;
- Direct smear preparation;
- Fixation and staining according to Papanicolaou.

Between the 1970s and 1990s, urinary cytology became an integral part of urological protocols, especially in monitoring recurrences of urothelial carcinoma. However, some limitations of conventional cytology gradually emerged:

- Poorly cellular specimens;
- Presence of blood and debris;
- Fixation artifacts;
- High interpretive variability;
- Low sensitivity for low-grade lesions.

These critical issues contributed to the frequent issuance of "atypical" or "indeterminate" reports, often associated with further invasive diagnostic investigations, such as cystoscopy.

The late 1990s and early 2000s saw the spread of liquid phase cytology (Liquid Based Cytology), initially developed for cervical screening and later applied to urinary cytology as well.

With the introduction of the LBC, the urine specimen is no longer swiped directly onto the slide, but collected and stored within a fixative solution specifically designed to preserve the cells. This seemingly technical change actually represented a real revolution in urinary cytology diagnostics. Indeed, immediate preservation of biological material allows cellular integrity to be maintained longer, reducing degenerative phenomena, drying artifacts and morphological changes that often complicated the interpretation of conventional preparations. Through centrifugation processes, the cells are then concentrated and evenly distributed on the slide, resulting in cleaner, more standardized and easily interpreted preparations.

One of the most important advantages of LBC is also the possibility of using the same biological specimen to perform additional tests, without the need for new patient samples. Indeed, ancillary tests such as:

- Immunocytochemistry;
- Molecular analysis;
- Urinary biomarker detection;
- Fluorescent hybridization techniques (FISH);
- Emerging genomic evaluations.

This integrated approach has transformed urinary cytology from a simple morphological examination to a multiparametric diagnostic platform, capable of combining traditional cellular observation and molecular medicine.

From the clinical point of view, the higher quality of preparations obtained with liquid cytology has helped to improve diagnostic reproducibility among operators and to reduce the number of specimens that cannot be evaluated or are classified as "atypical." This has had tangible repercussions in the management of the patient with bladder cancer, favoring more accurate follow-ups and better selection of cases truly deserving of invasive investigations such as cystoscopy.

During the 2013 International Congress of Cytology, held in Paris, an international group of experts initiated the development of a standardized system for urinary cytology reporting.

The main goal was to reduce:

- The diagnostic variability;
- The excess of vague categories;
- The poor clinical correlation of many cytology reports.

The focus was shifted to the identification of high-grade urothelial carcinoma (HGUC), which was considered more clinically relevant.

In 2016, the first official edition of The Paris System for Reporting Urinary Cytology (TPS) was published.

The introduction of The Paris System for Reporting Ur inary Cytology (TPS), officially published in 2016, represented a major step forward in the standardization of urinary cytology. Prior to the TPS, in fact, reporting was often heterogeneous and characterized by the overuse of unspecific terms such as "atypia," resulting in interpretation and management difficulties.

The TPS introduced rigorous and agreed morphological criteria, focusing mainly on the identification ofHigh-Grade Urothelial Carcinoma (HGUC), i.e., the most clinically aggressive and relevant form. The diagnostic evaluation is based on well-defined cellular parameters, such as nucleus/cytoplasm ratio, nuclear hyperchromasia, and nuclear membrane irregularities.
The system has also defined standardized diagnostic categories, including:

- Negative for High-Grade Urothelial Carcinoma (NHGUC )
- Atypical Urothelial Cells (AUC)
- Suspicious for HGUC (SHGUC)
- High-Grade Urothelial Carcinoma (HGUC)

Adoption of the TPS has improved diagnostic reproducibility and communication between cytopathologist and urologist, reducing overuse of the "atypical" category.

In 2022, the second edition of The Paris System was published, with updates based on scientific evidence accumulated in the years since the first publication. The updates included:

- Refinement of diagnostic criteria;
- Better definition of atypical categories;
- Integration with new molecular knowledge;
- Correlation with clinical risk.

Cystoscopy still represents the gold standard in the diagnosis and follow-up of bladder cancer, but it remains an invasive, expensive procedure that is not always well tolerated by patients, especially when repeated over time. In this context, the evolution of urinary cytology - made more accurate and standardized through liquid phase cytology (LBC) and TPS, and supported by the use of urinary biomarkers - has had a significant clinical impact.

In fact, more reliable cytology allows better selection of patients who are truly at risk, reduces false positives and ambiguous reports, and allows optimization of follow-up pathways. As a result, the number of unnecessary cystoscopies is reduced, directly benefiting patient quality of life and the overall sustainability of diagnostic pathways.

Today, this integration of LBC, TPS, and biomarkers is one of the pillars of precision medicine in urothelial carcinoma. Future development of the discipline is also moving toward digital pathology, artificial intelligence, automated image analysis, and the use of genomic and proteomic biomarkers, with the goal of making follow-up increasingly personalized, early, accurate, and less invasive.

Overall, the path started with conventional cytology has progressively transformed the management of bladder cancer, concretely improving both the diagnostic efficacy and quality of life of patients.

In the month dedicated to bladder cancer awareness, to retrace the evolution of urinary cytology is to recount not only the progress of a diagnostic technique, but also the change in the way this disease is addressed today. From conventional cytology to the liquid phase, to the standardization introduced by The Paris System and the new perspectives offered by artificial intelligence and molecular biomarkers, each step forward has helped make diagnosis more accurate, follow-up less invasive, and patient management more personalized.

To talk about diagnostic innovation during Bladder Cancer Month is therefore to emphasize how much research, technology and standardization can translate into concrete benefits for patients: fewer unnecessary procedures, more timely diagnosis and a better quality of life. And it is precisely this continuous evolution in diagnostic medicine that today makes it possible to look to the future with increasingly effective tools in the fight against urothelial carcinoma.