Urothelial cells in smears from cervix uteri.

OBJECTIVES: To establish the cytological criteria to identify the urothelial cells in cervical smears in order to avoid mistakes in the cytological diagnosis.
MATERIALS AND METHODS: Cervical smears from 34 post menopausal women with vesicovaginal fistulas, advanced bladder prolapse and genital erosive lichen planes (vulvar kraurosis) (Group 1) and transitional cell metaplasia of the cervix (TCM, Group 2) were stained with Papanicolaou technique. The cervical samples were taken during the routine annual examination for prevention of the uterine cancer.
RESULTS: The smears of cervix from Group 1 showed urothelial cells from the three layers of the transitional epithelium. The umbrella cells are the bigger ones with relatively large nuclei. Frequently, they are multinucleated with single or multiple nucleoli and a typical "frothy" cytoplasm (cytoplasmic vacuoles). The cells of the Group 2 showed nuclei with oval to spindled shapes, some tapered ends, less cytoplasm than squamous metaplastic cells, powdery chromatin, small nucleoli and nuclear grooves.
CONCLUSIONS: The umbrella cells may be mistaken for dysplastic cells originating in low grade squamous intraepithelial lesions lesions (LSILs) due to their nuclear and cytoplasm sizes. Therefore, it is important to know the possibility of their appearance in the cervical smears, especially in post menopausal patients in order to avoid a false diagnosis of an intraepithelial lesion. It is unlikely that deeper cells of urothelium would be confused with high grade squamous intraepithelial lesion (HSIL) cells. However, their presence might be a reason of mistake in the diagnosis. TCM is an under-recognized metaplastic phenomenon of the cervix and vagina, which is a mimicker of high-grade squamous intraepithelial lesion. The differential characteristic between umbrella cells, cells from TCM and the deeper urothelial cells, and LSIL and HSIL are detailed in the present paper.

Introduction

The finding of urothelial cells in the smears of uterine cervix is a very infrequent event. Some pathologies associated with this case are: Vesicovaginal fistulas and advanced bladder prolapse. The main cause of vesicovaginal fistulas is necrosis in the childbirth channel with important injury in the pelvic floor causing ischemia to the tissue.[1-6]

Other cause for the presence of urothelial cells in vagina is the genital erosive lichen planus with vaginal involvement including partial obliteration of the vagina. The clinical picture is that of continuous dripping of tinkles through the vagina with concomitant irritation of the vulva, vagina and perineum.[7] These pathologies produce urinary incontinence, contaminating with urine the material obtained of vagina. So far, as we know, it is the first report about the presence of urothelial cells in smears taken for routine cytology of uterine cervix (Pap test) except a case shown in the Papanicolaou atlas[8] and a reference by Koss et al.[9]

Transitional cell metaplasia (TCM) of the cervix is rarely reported in the pathology literature. Many of the cases could have been confused with squamous dysplasia due to the lack of apparent maturation. However, in most cases, attention to cytological detail disclose the typical features of transitional cell metaplasia. This process, usually seen in older women, can be over diagnosed as high grade squamous intraepithelial lesion (HSIL) leading to unnecessary treatment.

As some of the cells in the lesions described above could be confused with squamous cells derived from intraepithelial lesions of the cervix uteri, the objective of the present paper is to establish the cytological criteria to identify the urothelial cells in order to avoid mistakes in the cytological diagnosis.

Materials and Methods

Thirty four women were chosen from 94,000 patients′ during 1998-2009. The cervical smears of the selected group showed urothelial cells. All the patients were post menopausal (50-82 years old, average 62.5). Twenty-one of them had advanced bladder prolapse, ten presented with vesicovaginal fistulas and one was diagnosed with genital erosive lichen planus (vulvar kraurosis) (Group 1). Two patients had transitional cell metaplasia (TCM) in the ectocervix and in transformation zone (Group 2).

Cervical smears taken of patients with low grade squamous intrepithelial (LSIL) and HSIL were used to compare the urothelial cells with dysplastic cells. All these patients had histological confirmed low-grade and high-grade squamous intraepithelial lesion. The cytology diagnosis was performed using the Papanicolaou technique.

Results

Group 1: The smears of cervix uteri showed urothelial cells from the three layers of the transitional epithelium: Deep, intermediate and superficial (umbrella cells). The deeper cells were small, polygonal or round, frequently grouped, with high nuclei/cytoplasm ratio, slight hyperchromatism and in some cases with cytoplasmic tails, especially when derived from renal pelvis. The cells from the intermediate layer showed the classical pyriform shape [Figure 1]. The umbrella cells were the bigger ones, frequently multinucleated with single or multiple nucleoli and a typical “frothy” cytoplasm (cytoplasmic vacuoles) [Figure 1c]. Normally, they have relatively large nuclei, probably the expression of polyploidy. In some smears, the images of the uterine samples were like the sediments of urine, but others showed isolated umbrella cells that resembled cells from LSILs [Figure 2].

Figure 1

(a) A multinucleated umbrella cell (top) and some squamous epithelial cells (bottom). Exocervical smear (Pap, ×400). (b) A multinucleated umbrella cell (centre, bottom). At the right, a cluster of deep cells from transitional epithelium. Exocervical smear (Pap, ×400). (c) Umbrella cells (one of them multinucleated) showing the typical frothy cytoplasm. Exocervical smear (Pap, ×400). (d) Cluster of deep urothelial cells. Exocervical smear (Pap, ×400)

Figure 2

(a) Cells infected by HPV. Three koilocytes are clearly visible, with viral nuclei and classic hallos. Exocervical smear (Pap, ×400). (b) Big cell exfoliated form LSIL. This cell is called “CIN 1 cell”: Note the granular, homogeneous and hyperchromatic chromatin. Exocervical smear (Pap, ×400)

Group 2: The exfoliated cells from TCM showed nuclei with oval to spindle shape, tapered ends, powdery chromatin, less cytoplasm than that of squamous metaplastic cells, small nucleoli and nuclear grooves. The nuclear size ranged from 1.5 to 3 times the size of an intermediate nucleus. Nuclear contours were wrinkled or regular [Figure 3].

Figure 3

Cells from transitional metaplasia of the cervix uteri. Note the characteristic grooves. Exocervical smear (Pap, ×1500)

Discussion

The umbrella cells may be mistaken for dysplastic cells of LSILs due to their nuclear and cytoplasm sizes; so it is important to know the possibility of their appearance in the cervical smears in order to avoid a false diagnosis of an intraepithelial lesion. This is especially important in the pathologies associated with post menopausal women. The urinary incontinence associated with prolapse explains the vaginal pollution with material proceeding from bladder and the appearance of cells of urothelial origin. The vesicovaginal fistulas are the cause of the traffic of urothelial cells to the vaginal cavity. These pathologies are the reflection of lack of skilled attendants at delivery in developing countries.[6] However, in our series, genital fistulae were as a result of complications from radiation treatment and gynecological surgeries (hysterectomy due to cervical cancer). In the genital erosive lichen planus, there are continuous drips of urine through the vagina.

LSILs in Pap smears are characterized by two cellular types that may or may not coexist: The classic koilocytes, pathognomonic cells of the Human papillomavirus infection (HPV) and the cells derived from CIN 1 (Richart).[10] The koilocytes have a characteristic “hallo”, which presents a clear cut between both cytoplasmic zones that it limits. The nuclei show typical smudged or blurry chromatin as a consequence of the viral cytopathic effect. The size of these cells and their nuclei are bigger than that of the intermediate normal cells of the squamous epithelium[11] [Figure 2a]. The “CIN 1” cells show an increase in N/C ratio and nuclear size, homogeneous or finely granular chromatin, small to medium size nucleoli, slight nuclear hyperchromasia and evenly stained nuclear membrane [Figure 2b]. The umbrella cells may be differentiated from the former cells because they have non-hyperchromatic and homogeneous nuclei with finely granular chromatin. In some cases, a more condensed cytoplasmic ring remembers to that of the koylocytes, but the limits of the hallo are slightly definite.[12] Table 1 shows the criteria to differentiate cells from LSILs and “Umbrella” from urothelium.

Table 1

Differential criteria among umbrella cells, CIN 1 cells and Koylocytes

LSIL is frequently encountered in young women; therefore, the umbrella cells in the samples from uterine cervix which are reported in post menopausal women should not present problems in their recognition. Nevertheless, cells with cytopathic effects by HPV (even koilocytes) in menopausal women medicated with estrogens have been reported.[13]

The cells of the deep layers of the urothelium with high N/C ratios might be confused with cells from HSIL′s. However, the fine granularity of the nuclear chromatin and the presence of round nucleoli demonstrate the benign characteristic of the urothelial cells. The cells from HSIL have large nucleus, irregular chromocentres with areas of irregular hetherochromatin, hyperchromasia and scant cytoplasm (high N/C ratios). They are frequently seen in clusters showing variability of nuclear sizes [Figure 4]. It is unlikely that deeper cells of urothelium would be confused with HSIL cells; Table 2 shows the differential criteria between the two cell types.

Figure 4

Cells exfoliated form HSIL. Exocervical smear (Pap, ×400)

Table 2

Differential criteria between cells from deep urothelial cells and HSIL

Transitional cell metaplasia (TCM) of the cervix is rarely reported in the pathology literature.[14-16] In our two patients, transitional cell metaplasia represented an incidental cytological finding [Figure 3]. It occurred in the ectocervix and in the transformation zone. The clinically significant lesion that can be confused with TCM is high-grade squamous intraepithelial lesion, especially CIS, due to the syncytial arrangement of the cell groups. In comparison with TCM, HSIL showed nuclei with high N/C ratios, hyperchromatic coarse chromatin and irregular nuclear contours. Grooves were absent [Table 3].[16]

Table 3

Differential criteria between cells from transitional cell metaplasia and HSIL

TCM is commonest in the fallopian tube, the ovary, broad ligament and vulva, resembling urothelium in all these sites.[15] Immunohistochemical endocrine markers like serotonin and calcitonin are shared between TCM of the vagina, cervix and urothelium.[17] However, the expression of these markers was not specific for TCM, because it was identified in normal cervical squamous epithelium and endocervix.

The shared embryogenesis of the early genitourinary systems would suggest that müllerian epithelium has the potential to differentiate into urothelium.[14] Most of the TCM express the urothelial immunophenotype Cytokeratin 7 and 20; this fact supports the former theory.[18] The factors responsible at the gene level for expression of this cell type are not known.

Conclusion

The knowledge of the presence of umbrella cells in the samples of uterine cervix can avoid false cytological diagnosis of LSIL. This must be considered especially in the samples of uterine cervix obtained from post menopausal women. It is unlikely that deeper cells of urothelium would be confused with HSIL cells. However, their presence might be a reason of mistake in the diagnosis. TCM, usually seen in older women too, can be over diagnosed as HSIL; so it is important to know the differential criteria between these pathologies.