Cytological findings of the micropapillary variant of urothelial carcinoma: a comparison with typical high-grade urothelial carcinoma

Cytologic features of micropapillary variant urothelial carcinoma in urinary tract cytology: Case series and review of literature

BACKGROUND

The micropapillary variant of urothelial carcinoma (MPVUC) is rare and aggressive. Surgical specimens often show atypical micro-clusters (AMCs) of cells with hyperchromatic, pyknotic, peripheral, irregular nuclei with variable nuclear to cytoplasmic ratios. We reviewed urinary tract cytology (UTC) from patients with MPVUC and hypothesized that AMCs would be present similar to those in surgical specimens.

METHODS

The archives were searched from 2000 to 2020 for patients with surgical cases with either MPVUC or conventional high-grade urothelial carcinoma (HGUC) and with prior abnormal UTC. Two pathologists reviewed UTC cases and controls in a blinded manner for AMCs, with quantitation of none, low, moderate, and high. Interrater reliability was compared by quadratic weighted Cohen's Kappa test. The association between numerical average score and MPVUC status was determined by logistic regression.

RESULTS

Five patients with invasive MPVUC, one patient with a noninvasive micropapillary component, and 15 control patients with conventional HGUC were included. All patients had prior or concurrent abnormal UTC samples. Increasing category of quantities of AMCs on cytology was associated with micropapillary status (OR 7.9, 95% CI 2.7-118, p = .045), with moderate agreement between raters (Cohen's Kappa 0.54, 95% CI 0.19-0.89, p = .004).

CONCLUSIONS

In patients with MPVUC on surgical specimen, AMCs were frequently observed on cytology. Similar atypical clusters were observed in patients with nonmicropapillary HGUC, albeit at lower frequency. However, given the WHO recommendation to diagnose micropapillary only if an invasive micropapillary component is present, a specific diagnosis of MPVUC on UTC cannot be based solely on the presence of AMCs.

Cyto-histo correlations of plasmacytoid and micropapillary variants of high-grade urothelial carcinoma: do they fit well in The Paris System for reporting urinary cytology?

INTRODUCTION

Plasmacytoid and micropapillary variants of high-grade urothelial carcinoma (HGUC) exhibit unique histologic morphology and very aggressive clinical behavior. However, the morphology of these 2 variants in urinary cytology is not well studied and evaluated using The Paris System for reporting urinary cytology.

MATERIALS AND METHODS

A database search was performed in all patients with the diagnosis of plasmacytoid or micropapillary HGUC. A total of 5 patients with positive urinary cytology cases were identified. The cytomorphology of every urinary cytology case was correlated with the histologic features in the surgical specimens from the same patient.

RESULTS

One urine and 4 bladder washings were evaluated. Cytologically, plasmacytoid HGUCs are characterized by single, large tumor cells with hyperchromasia, irregular nuclear membranes, and vacuolated cytoplasm. The nuclear-to-cytoplasmic (N:C) ratio was less than 0.5 in many of the malignant cells due to the abundant cytoplasm. The cytology features of micropapillary HGUC include the presence of micropapillae of tumor cells with no fibrovascular core. Individual high-grade urothelial cells were also identified in all 4 cases, but 1 (25%) of these had only rare cells meeting The Paris System criteria for HGUC due to abundant cytoplasm and lack of hyperchromasia in most malignant cells.

CONCLUSIONS

Plasmacytoid and micropapillary variants of HGUC have unique cytomorphologic features in urinary cytology specimens, which are reflective of the corresponding histological findings. These 2 clinically aggressive variants of HGUC may not be as readily interpreted as malignant using The Paris System for reporting urinary cytology, creating potential diagnostic pitfalls.

Diagnostic utility of double immunostaining of a urine cytology preparation for cytokeratin 20/p53 expression in a young woman with micropapillary urothelial carcinoma of the renal pelvis presenting as an unknown primary malignancy

Atypical urine cytology (CYT) triggers a cystoscopic or another ancillary investigation that targets urothelial neoplasms. We report a case presenting as an unknown primary malignancy, which illustrated the diagnostic utility of direct double immunostaining for cytokeratin 20 (CK20)/p53 expression in a urine CYT specimen. A 42-year-old woman visited the emergency room for pain in her right lower abdominal quadrant. Computed tomography revealed postrenal obstructive hydronephrosis, and her urine CYT showed malignancy, type undetermined. Atypical cells that are positive for cytoplasmic expression of CK20 and nuclear expression of p53 could facilitate the decision to perform a nephroureterectomy for urothelial carcinoma.

A case report of urothelial carcinoma with combined micropapillary and plasmacytoid morphology in the urinary bladder

A case of combined micropapillary and plasmacytoid urothelial carcinoma (UC) of the urinary bladder is presented for a 74-year-old male who was admitted to the hospital with gross hematuria and multifocal papillary bladder tumors. Abdominal computed tomography showed a large enhancing mass on the left lateral and anterior wall of the urinary bladder, which was highly suspicious for extravesicular extension and focal extension of the anterior lesion to the pubic bone. In voided urine, cancer cells were scattered as micropapillae or nests as well as single cells on the low power view. On a higher power view, micropapillae or nests were composed of pleomorphic, high grade tumor cells with an inverted nuclear arrangement and with acinar structures occasionally identified. Single cells were discohesive and large with a thick cytoplasm and eccentrically located nuclei. Histologically, the tumor from the resected bladder showed diffusely infiltrating micropapillae or nests with a surrounding halo and dense singly-scattered plasmacytoid cells. Immunohistochemically, the cancer cells were positive for cytokeratin-7 and cytokeratin-20 but negative for S-100, leukocyte common antigen, and vimentin. At the time of radical cystectomy, severe adhesions and peritoneal metastases were found and the surgery was discontinued. The patient received systemic chemotherapy, but died of bladder cancer 14 months after surgery.

Cytological features of lung adenocarcinoma with micropapillary pattern in the pleural or pericardial effusion: analysis of 5 cases

Micropapillary pattern is a distinct histopathological pattern, and usually shows a high frequency of lymphatic invasion and lymph node metastases. This pattern is also reported in lung adenocarcinoma, however, only one cytological report of lung adenocarcinoma with micropapillary pattern has been reported. In this study, we analyzed the cytological features of this type of carcinoma in the pleural or pericardial effusion. This study was comprised of 5 consecutive cases of lung adenocarcinoma with micropapillary pattern, in which the tumor cells were present in the pleural or pericardial effusion and whose diagnoses were histopathologically confirmed. The characteristic cytological findings in the pleural or pericardial effusion were as follows: i) tightly cohesive small nests of tumor cells showing papillary structure without fibrovascular core, ii) these nests were comprised of approximately 5-20 tumor cells, iii) cauliflower-like and acinar-like structures were also observed, iv) intracytoplasmic vacuoles were observed in 40% of the cases, and v) the neoplastic cells had large round to oval nuclei containing coarse chromatin and occasional conspicuous nucleoli. It has been reported that the presence of micropapillary structure and intracytoplasmic vacuolation are also characteristic cytological features of micropapillary carcinoma of the urinary bladder, therefore, they are thought to be common cytological features of carcinomas with micropapillary pattern. Consequently, detection of these features can lead to a cytodiagnosis of lung adenocarcinoma with micropapillary pattern in the pleural or pericardial effusion. Recognition of these features is important because this type of tumor shows an aggressive clinical course.