Cytological techniques are instrumental in the detection and diagnosis of malignant tumors of the urinary system. Cytology is used to examine cells from urine and is useful in the diagnosis of urinary tract infections, tumors and other diseases.
In 1858 Rudolph Virchow founded the cellular study known today as cytopathology; the study of the cell became known as cytology to then include the Pap smear as a screening tool for early detection of cancer. Cytopathology can be used to examine almost all organ systems in the body, including body fluids particularly. Urine cytology is one of the most difficult disciplines in pathology. In most cases urothelial cells are divided into four categories: 1) normal, 2) atypical, 3) suspicious and 4) malignant. As well, several infections can cause abnormalities that can resemble cancer in urine cytology.
The study of urine cells is one of the oldest medical methods of medical practice. Egyptians discovered that blood in the urine later indicated a bladder disorder identified as a cancer known as Schistosoma haematobium. Simply collecting a urine specimen and examining it grossly was a routine medical test. Urine is primarily water. The color of urine provides a great deal of medical information that can be helpful in some diagnoses. Usually a normal urine sample may be clear or straw-colored or a pale yellow; a colorless urine can be a sign of over-hydration; dark yellow urine can indicate
dehydration; bloody urine is considered hematuria; dark orange or brown color may indicate jaundice or Gilbert's disease; and a black colored urine may stem from a melanoma and called melanuria.
Food can often give color to the urine. For example, beets can give urine a pink color and asparagus can give urine a green color. Turbid or cloudy urine is usually a symptom of a bacterial infection or a crystallization of calcium phosphate salts. The pH of urine should be about 4.6 -- 8 and 7 is neutral.
Urine is usually a sterile liquid secreted by the kidneys and may contain epithelial cells from the urinary tract. Cytology of urine has been instrumental in the identification of viral infections such as human polyomavirus. Here, we explore how urine cytology may be the most vital diagnostic technique in urinary medicine.
Primary pathogens such as Blastomyces dermatitidis and Cryptococcus neoforms can be detected in cytological techniques. Blastomycosis is a fungus that produces lesions and abcesses in the skin, then works its way to other organs. The yeast forms of this organism are spherical, have a thick, refractile cell wall and can be similar or larger than cryptococcus. These organisms may be engulfed by macrophages or found simply "free floating."
Special stains such as Periodic Acid Schiff -- Light Green or Grocott's Methenamine Silver can be used to demonstrate most blastomycosis organisms. The PAP stain will demonstrate this organism (Fig. 1, 40 X).
Cryptococcus can be found in patients with HIV. The detection of the capsular material can be seen by cultures of CSF, sputum and urine. Cryptococcus neoformans has a definite form -- spherical buds that measure from 5 to 25 microns in diameter and a thick, sharply defined capsule. Special stains that will faintly demonstrate the organism are the Papanicolaou and Diff Quik but the stains of choice are Periodic Acid Schiff - Light Green or the classic Mayer's Mucicarmine (Fig. 2, 40 X.)
Usually the identification of crystals in the urine is performed by a microscopic urinalysis assay. Many crystals are identified by their color, shape and the pH of the urine sample. The absence or presence of crystals in a urine specimen can be a diagnostic tool in the treatment of disease. Crystals usually are divided into medication, disease indicators or normal occurrence. Radiological dyes can produce crystals and certain drugs such as sulfonamides can also form specific crystal structures (Fig. 3A, Papanicoloau stain, 40 X). Urate crystals can be found in improperly fixed urine specimens. The pH of the urine can change the precipitation of urates. The crystals have different shapes and have no real diagnostic purpose. Most crystals will polarize with standard microscopic polarization (Fig. 3B, 40 X).
Urothelial Cell Carcinoma
Urothelial cell carcinoma (UCC) usually occurs in the kidney, urinary bladder and other organs. UCC is the most common type of cancer in the urachus, ureter and urethra and is the second most common type of kidney cancer.
Interestingly, UCC is usually caused from environmental sources. Workers in the petroleum industry, manufacture of paints and aniline dyes and agriculture chemicals can be exposed to chemicals that can contribute to urothelial cancer.
A classic feature of urothelial cells can be the unique design or "cluster" they can form, which can be small and flat and composed of a few cells. The clusters also can be oval, sphere-shaped or "papillary" or minute projection. Umbrella cells can be seen lining the periphery of the cluster. Urothelial cancer can be seen in bladder washing techniques demonstrating a papillary cluster (Fig. 4, Papanicoloau stain 40 X).
Reactive Epithelial Cells
Epithelial cells form the epithelial tissue that lines body cavities and covers organs. The walls of the bladder are lined with stratified transitional epithelium, which allows the bladder to expand. Urothelial cells, a type of epithelial cell found only in the urinary tract, become reactive when injured by inflammation; they literally react to the presence of inflammation. In catheterized urine, a large cluster of degenerated, benign reactive cells can exhibit a low nuclear to cytoplasmic ratio and the nuclei can be irregular in contour. The nuclei can be small and hyperchromatic. Fig. 5 (Papanicolaou stain, 40 X) is an example of reactive urothelial cells from a bladder washing.
Atypical Low Grade Papillary Carcinoma
Atypical cells are irregular or unusual, perhaps even abnormal; however, they may not be cancerous. Several factors can make normal cells appear atypical such as inflammation, normal aging and infection.
Urine cytology is an essential agent for the detection of urothelial neoplasia. The accuracy of urine cytology depends on factors related to the tumor grade, type of specimen and proper sampling. An example of atypical low grade papillary carcinoma is shown in Fig. 6 (Papanicolaou stain, 40 X).
Hemosiderin results from breakdown of hemoglobin and is a yellow-gold crystalline pigment. Reactive urothelial cells in voided urine and hemosiderin in the cytoplasm can be seen in laden macrophages (Fig. 7, Papanicolau stain, 40 X). Granules of hemosiderin can be engulfed by macrophages and so abundant that they mask the nucleus (Fig. 8, hemosiderin laden macrophages).
Hemosiderinuria, also known as "brown urine," occurs with chronic intravascular hemolysis where hemoglobin is released from the red blood cells in the bloodstream in excess. Excess hemoglobin is filtered by the kidney and re-absorbed in the proximal tubule; the iron is then extracted and stored in ferritin, also known as hemosiderin.
Cells of the proximal tubule drop off with the hemosiderin, are excreted into the urine and can be seen in a few days after the onset of hemolytic conditions. Hemosiderin granules in the urine can serve as an aid in the diagnosis of pernicious anemia and hemochromatosis. Figs. 9A and 9B show hemosiderin laden macrophages with hemosiderin demonstrated by the Prussian Blue Reaction special stain.
The presence of bacteria in the urine is referred to as bacteriuria. Left untreated, a urinary tract infection will develop. Many microorganisms can be detected by cytology techniques primarily in the urine, spinal fluid or other body fluid. Some examples of bacteria are Chlamydia, Klebsiella pneumoniae, Escherichia coli and Enterococcus faecalis. Obstructive processes such as prostate enlargement, calculi, strictures, compression, calculi or diverticula can interfere with the flow of urine and cause infection (Fig. 10, Papanicolaou stain, 40 X).
M. Lamar Jones is with the Department of Pathology, Emory University Hospital Atlanta, GA, and program director, School of Histotechnology, Davidson County Community College, Lexington, NC.