Fine needle aspiration cytology of metastatic urothelial carcinoma: Study of seven cases with review of literature.

BACKGROUND: Metastatic urothelial carcinoma (UC) is rarely described in cytology literature. Appropriate cytological diagnosis is important in certain clinical scenarios to exclude a second primary. AIMS: To delineate cytological features that are helpful in diagnosing metastatic UC.
MATERIALS AND METHODS: The study included seven male patients with age range of 48 - 72 years. These patients were diagnosed cases of UC and had now presented with lesions in liver, lungs, bones or lymph nodes. Computed tomographic (CT)/ultrasonographic (USG) guided fine needle aspiration cytology (FNAC) was available from one of these sites.
RESULTS: Cercariform cells (CCs) could be identified in five out of seven cases. In four cases, multilayered papillary fragments (MPFs) were identified which were reminiscent of histopathologic appearance of UC. One of these two morphologic features was present in all the cases. However, both CC cells and MPFs were present only in two cases.
CONCLUSION: Previous clinical history is indispensible while diagnosing metastatic UC. MPFs and CC cells are strong morphologic clues to urothelial origin. In poorly differentiated tumors, differentiation from other epithelial tumors may not be possible on the basis of morphology alone.

Introduction

Fine needle aspiration cytology (FNAC) is being increasingly used for diagnosis of primary as well as metastatic tumors occurring at various sites. In patients with known primaries, FNAC diagnosis of metastatic tumors avoids unnecessary surgeries. Urothelial carcinomas (UCs) are common and may show metastasis to lymph nodes, lungs, bones, and liver.[12] However, FNAC from metastatic UCs are rarely encountered in clinical practice.[3] Few studies have described cytological features of these tumors and their distinction from other tumors. Accurate cytological diagnosis is essential to exclude the possibility of second primaries.

In this paper, we highlight cytological features in seven cases of metastatic UC and compare the findings with those reported in literature. The aim of the study is to delineate cytological features that are helpful in arriving at diagnosis of metastatic UC.

Materials and Methods

Seven cases of metastatic UC of bladder seen over a period of three years (March 2008 to March 2011) were retrieved from the records of cytopathology laboratory of our institution. The patients were all males in the age range of 48 to 72 years; and had been treated for carcinoma of urinary bladder six months to six years earlier. All were biopsy proven cases of UC of bladder. However, detailed histopathologic features (grade of tumor, status of muscle invasion) were available in three cases only. These patients had presented to the hospital for breathlessness, bone pains, or vague symptoms. Radiological investigation revealed space occupying lesions in lung or liver, lytic lesions in bones or enlarged lymph nodes [Table 1] and suspicion of metastatic tumor was raised. Computed tomography (CT) or ultrasonography (USG) guided FNAC was done and both May-Grünwald-Giemsa (MGG) and Papanicolaou stained slides were prepared.

Table 1

Clinical history of cases

FNAC smears from all cases were reviewed and various cytological parameters were studied [Table 2]. A search was especially made for cercariform cells (CCs). These were identified using the definition of Renshaw et al.[4] Cells with nucleated globular body and cytoplasmic tails (long and thin or short and broad) with flattened or bulbous ends were labelled as CCs. Only single cells were considered. Cells within the groups were not considered while counting CCs. CCs were counted in 10 high power fields (40×) each having a minimum of 10 cells.

Table 2

Cytologic features of metastatic urothelial carcinoma

Results

Smears in all cases were moderate to highly cellular. Papillary fragments and syncitial clusters were seen in all the cases [Table 2]. Papillary fragments without fibrovascular core were more frequent compared with those with a vascular core. In four of the seven cases, papillary fragments with or without vascular cores and lined with multiple layers of tumor cells (multilayered papillary fragments) were present. These were reminiscent of histopathologic appearance of UC [Figure 1]. Many single cells were present in the background in all but one case (Case 5, [Table 2]). Within the syncitial groups and papillary fragments columnar cells could be identified in all seven cases (occasional in case 7).

Figure 1

Multilayered papillary fragments (Pap, ×200)

The tumor cells were predominantly round to oval with moderately pleomorphic nuclei in all the cases. The nuclear chromatin was vesicular and nucleoli when present were small and multiple [Table 2]. The cytoplasm was scant (case 5and7) to abundant and vacuolated (cases 1, 2, 3, 4, and 6). Multinucleated tumor cells were identified in cases 3 and 4.

CCs [Figure 2] were identified in five out of seven cases. In all these cases, at least 10 or more CCs were present. The minimum and maximum number of CCs were 10 (case 1) and 40 (case 4). Tumor in case 3 showed necrotic cells lying singly in the background; hence one could not be certain of CCs. No squamous differentiation could be observed in any of the cases.

Figure 2

Cercariform cell, see black arrow (Pap, ×600)

Discussion

UC are not uncommon in India. According to population based cancer registries, it is one of the ten leading cancers in urban population of Delhi.[5] Muscle invasion is present in 30% of patients with bladder cancer. This subset of patients has a high risk of death from distant metastasis.[2] Distant metastasis in cases with superficial papillary bladder cancer is extremely unusual.[67] Regional lymph nodes, lungs, liver, bone, and adrenal glands are most common sites of metastases of urothelial tumors.[1] UC metastasis has also been described at unusual sites as skin, orbit, endocardium, and duodenum.[8-11] FNAC of UC is however rarely encountered in cytology practice and only few studies describing the cytological features of metastatic UC are available on literature search [Table 3].

Table 3

Review of Literature

Presence of numerous CCs in smears is considered to be a strong diagnostic clue towards urothelial origin. Powers and Elbadawi[17] first described CCs as cells with long cytoplasmic tail and flattened ends. Renshaw et al.,[4] expanded this definition to include cells with shorter, broader, but flattened and often bulbous tail. They also described a vacuole in bulbous tail of these cells to be a useful feature in identifying CCs. The nucleus of CCs was always eccentrically placed and could be of low or high grade. Binucleated or rarely multinucleated CCs were also observed. They excluded cells in clusters while identifying CCs since the cytoplasmic flattening could be an artefact due the close proximity of surrounding cells. In their study, they compared 14 cases of metastatic UC with 22 cases of non-small cell lung carcinoma (NSCLC). They observed that CCs were often present (eight out of nine cases) and abundant (>10 per case) in cases of UC without squamous differentiation, but were not present in any of the UC with squamous differentiation. In NSCLC, the CCs were present, but were less than 10 per case.

Hida and Gupta[15] studied 11 cases of metastatic UC and compared them with 45 cases of poorly differentiated malignant epithelial neoplasm (PDMEN). They observed that CCs were present in all cases of metastatic UC and in 16 out of 45 cases of PDMEN. However, numerous CCs (> 20/case) were more likely to occur in metastatic UC (5/11 cases) as compared to PDMEN (2/45 cases).

We could identify CCs in five out of seven cases. Ten or more CCs were present in the background in each of these cases. We observed cells with long thin and short broad tail. The tail ends were flattened or bulbous. Vacuole in bulbous tail was not a conspicuous feature in any of our cases. In case 3, the cells in the background were mostly necrotic; hence it was not possible to comment on CCs. In case 5, no single cells were present in the background.

The tumor cells in all our cases were present in syncitial clusters and papillary fragments with or without fibrovascular cores. Papillary fragments made of multiple layers of tumor cells arranged with or without fibrovascular core (multilayered papillary fragments, MPFs) were present in four out of seven cases. These fragments recapitulated the histopathologic appearance of UC.

Case 5 presented with a large solitary FDG –avid lung mass and clinico-radiologic suspicion of second primary was high in this case. Although no CCs were identified in this case, the presence of MPFs lying in a clean background favored the diagnosis of a metastatic UC.

In our study, all the cases were known case of UC. In the absence of clinical history, it would have been difficult to suspect urothelial origin in case 1, which morphologically resembled papillary adenocarcinoma, and cases 6 and case 7, which mimicked poorly differentiated adenocarcinoma. Except for the presence of CCs, there was no other clue towards urothelial differentiation in these cases. In rest of the cases, the presence of MPFs was the most striking morphologic pointer. Both MPFs and CCs were present in two of the seven cases (case 2 and case 4).

We did not find squamous differentiation in any of the seven cases. However, squamous differentiation is not uncommon in high grade UC and it may be difficult to differentiate squamous cell carcinoma from UC with squamous differentiation.

Layfeild et al.,[16] statistically analyzed 37 cytological features to recognize urothelial differentiation in a series of 26 metastatic UC, 10 metastatic squamous cell carcinomas, and 15 metastatic adenocarcinomas. They found that combination of five variables (waxy metaplastic cytoplasm, cercariform cells, spindle shaped cells, multiple nucleoli, and columnar shaped cells) accurately predicted 90% of all diagnoses. They suggested that the presence of single nucleoli and columnar shaped cells favored a diagnosis of adenocarcinoma over UC. However, columnar cells could be identified within the tumor cell groups in all our cases. The number of columnar cells present within the tumor cell groups varied in different cases as these were numerous in case 2 and occasional in case 7.

Cantley et al.,[1] in a recent review on cytological diagnosis of metastatic UC have also emphasized that no single cytological feature can distinguish UC from other mimics.

Immunohistochemical staining has been tried with variable results. Co-expression of CK 7 and CK 20 has limited diagnostic utility in differentiating UC, adenocarcinomas, and squamous cell carcinomas. Kaufman et al.,[18] reported that uroplakin III is positive in 53% of metastatic UC and is not detected in any other epithelial neoplasm. Parker et al.,[19] confirmed these results and found UPIII expression in 57.1% of metastatic UC, but no expression in non-urothelial neoplasm. They suggested an antibody panel of UP III, thrombomodulin, high molecular weight cytokeratin, and CK 20 may be helpful in diagnosing metastatic UC with cytological features overlapping with other epithelial neoplasm. Immunostaining using these markers was not done in the present study.

Conclusion

In conclusion, cytological diagnosis of metastatic UC can be made on the basis of presence of multilayered papillary fragments along with appropriate clinical history. Even in the absence of a clinical history, their presence should raise suspicion of a possible urothelial primary. CCs are strongly associated with UC, but a diagnosis of UC can be made even in their absence. In poorly differentiated cases, differentiation from other epithelial neoplasm is not possible on the basis of morphology alone. Newer specific markers like UP III might be helpful in these cases.