Bladder Large Cell Neuroendocrine Carcinoma(LCNEC): A Case Report of Exfoliated Cytology and Pathological Characteristics

Summary

Here, we present a standardized diagnostic protocol that integrates urine cytology, histopathology, and immunohistochemistry for diagnosing primary bladder large-cell neuroendocrine carcinoma in elderly patients.

Abstract

Primary large cell neuroendocrine carcinoma (LCNEC) of the bladder is an extremely rare and highly aggressive malignancy with a poor prognosis, bringing major challenges to clinical diagnosis and treatment. We report the case of a 77-year-old man who presented with recurrent gross hematuria for more than 8 months, accompanied by urinary frequency, urinary urgency, and lumbosacral pain. Imaging revealed a large soft-tissue mass on the posterior bladder wall without pathognomonic imaging findings. Urine exfoliative cytology revealed atypical tumor cells with large cellular size, high nucleocytoplasmic ratio, scant cytoplasm, and marked nuclear atypia. Given the advanced age and multiple underlying comorbidities, the patient underwent transurethral resection of the bladder tumor. Histopathologically, the tumor was arranged in diffuse sheets with organoid architecture, composed of large polygonal cells with prominent atypia, active mitosis, focal necrosis, and intravascular tumor thrombi. Immunohistochemically, CK-Pan showed a paranuclear punctate expression pattern; neuroendocrine markers INSM1, Syn, and CD56 were diffusely positive; Ki-67 showed a high proliferation index; and P53 displayed diffuse strong expression. The final diagnosis of primary bladder LCNEC was confirmed by integrated morphological and immunohistochemical findings, with preoperative contrast-enhanced CT defining an advanced clinical stage of cT3N0M0 (American Joint Committee on Cancer, AJCC 8th edition). The patient received postoperative adjuvant chemotherapy, and tumor recurrence was identified at the 3-month follow-up with a stable general condition during the observational period. This case indicates that bladder LCNEC lacks specific clinical and imaging manifestations. Urine exfoliative cytology is a valuable non-invasive ancillary tool for detecting high-grade malignant cells in the urinary tract, whereas combining histopathology and immunohistochemistry remains the gold standard for definitive diagnosis. Surgical resection combined with individualized chemotherapy constitutes the main therapeutic regimen, and close long-term follow-up is indispensable for this highly aggressive tumor. Further clinical studies are required to optimize therapeutic strategies and improve patient prognosis.

Introduction

Bladder cancer includes a variety of histological subtypes, among which primary neuroendocrine carcinoma of the bladder accounts for less than 1% of all bladder cancers. According to the WHO 5th Classification of Tumors of the Urinary System and Male Genital Organs, bladder neuroendocrine carcinoma is divided into four subtypes: small cell neuroendocrine carcinoma (SCCB), large cell neuroendocrine carcinoma (LCNEC), well-differentiated neuroendocrine tumor, and paraganglioma. Most bladder neuroendocrine carcinomas are of the small cell type, while primary bladder LCNEC is an extremely rare, high-grade neuroendocrine carcinoma characterized by strong invasiveness, rapid progression, and high risk of metastasis. It is typically diagnosed at an advanced clinical stage and is associated with an extremely poor long-term prognosis^1,2. Due to its low incidence, non-specific clinical manifestations and imaging features, and the scarcity of published clinical data, the diagnosis and management of bladder LCNEC remain challenging.

Compared with pelvic computed tomography, cystoscopy, and surgical biopsy, urine exfoliative cytology is non-invasive, inexpensive, and suitable for preliminary detection of malignant cells and postoperative follow-up, especially for elderly patients with multiple underlying diseases who cannot tolerate invasive examinations, although it cannot define tumor staging alone.

We admitted an elderly patient with bladder LCNEC recently and report it as follows, aiming to improve clinicians’ awareness of this rare disease and provide a reference for the standardized diagnostic workflow of this tumor.

Case presentation:

A 77-year-old male patient was admitted on November 16, 2024, presenting with recurrent gross hematuria lasting more than 8 months. He had moderate-volume gross hematuria with occasional blood clots, accompanied by urinary frequency, urinary urgency, and lumbosacral pain, but no dysuria, abdominal distension, chills, or fever. Symptoms relapsed after empirical anti-infection and hemostatic treatment. The patient had a history of chronic obstructive pulmonary disease and cerebral infarction with residual left limb motor dysfunction, without drug allergy or previous surgical history. No obvious body weight loss was noted during the disease course.

Physical examination on admission

Vital signs on admission were as follows: body temperature 36.6 °C, heart rate 82 beats/min, respiratory rate 20 breaths/min, and blood pressure 140/79 mmHg. Physical examination revealed a barrel chest without abnormal pulmonary rales. The abdomen was flat and soft, with no tenderness, rebound tenderness, palpable mass, or shifting dullness. No percussion tenderness was detected over the kidneys. There was no tenderness in the bladder and ureteral regions, and no bleeding was observed at the external urethral orifice. Digital rectal examination revealed grade II benign prostatic hyperplasia without palpable pelvic masses or abnormal rectal bleeding.

Preoperative chest and abdominopelvic contrast-enhanced CT demonstrated a bulky soft-tissue lesion originating from the posterior bladder wall, with suspected transmural bladder wall infiltration and imaging manifestations suggestive of possible extravesical tumor extension, accompanied by left ureteral ostial involvement. No pelvic lymphadenopathy or distant organ metastatic lesions were detected on full-thoracoabdominal imaging. Accordingly, the patient’s tumor was assigned a clinical TNM stage (cT3N0M0) based on the AJCC 8th edition bladder cancer staging criteria. Notably, only fragmented tissue specimens were obtained via transurethral resection of bladder tumor (TURBT), which lacked intact full-thickness bladder wall tissue; therefore, formal pathological pTNM staging could not be completed postoperatively.

Diagnosis, assessment, and plan:

Given the patient’s recurrent gross hematuria and clinical manifestations, imaging was initially arranged to identify intravesical lesions. Routine urine testing and exfoliative cytology of urinary sediment were also performed to screen for malignant cells. Given the patient’s advanced age and cardiopulmonary comorbidities, combined with poor surgical tolerance, transurethral resection of bladder tumor (TURBT) was scheduled to achieve hemostasis and clarify the pathological nature of the lesion. Postoperative histopathological and immunohistochemical examinations were arranged to confirm the final diagnosis and guide the formulation of the subsequent treatment strategy.

Protocol

This study was approved by the Ethics Committee of the affiliated hospital (Approval No. 2026-015) and supported by the 2025 Science and Technology Personnel Training Project of Fujian Provincial Department of Science and Technology (Grant No. 2025350709). Written informed consent was obtained from the patient and his family prior to all clinical examinations and surgical interventions.

All reagents, instruments, and consumables used throughout this protocol are listed in the separately uploaded Table of Materials.

1. Imaging examination

1. Chest and whole abdominal computed tomography (CT) was performed using a 64-slice spiral CT scanner. The scanning parameters were set as follows: 120 kVp, field of view 37.5 × 37.5 cm, slice thickness 5.0 mm. Iterative reconstruction was applied, and multiplanar reconstruction (MPR) was performed in coronal and sagittal planes to evaluate bladder wall lesions, tumor scope, and potential distant organ metastasis.
2. All imaging data were independently interpreted by two senior radiologists, and a unified diagnostic conclusion was reached through consensus discussion.

2. Urine examination and exfoliative cytology detection

1. Routine urine examination was completed to detect the levels of urine bilirubinogen, ketone body, occult blood, protein, and other indicators, and observe the physical and chemical properties of urine.
2. For urinary sediment exfoliative cytology examination (Wright-Giemsa staining), urine was centrifuged at a relative centrifugal force of 400 g for 5 min at room temperature, the supernatant was aspirated and discarded, and 0.2 mL of urinary sediment was retained for smear preparation.
3. Smear preparation was performed according to the blood smear method, with reference to viscosity. After the smear was air-dried naturally, Wright-Giemsa staining was performed: Solution A was applied to the smear for 3 min of fixation, then Solution B buffer was added at a 1:2 ratio and incubated for 5 min.
4. For washing, slow, parallel-running tap water was used for 2 min; avoid direct vertical flushing of the smear surface and excessive washing time to prevent cell shedding and staining fading. Do not pour off the staining solution before rinsing.
5. The stained smears were observed under a light microscope by two senior cytologists, and the morphological characteristics of cells were recorded and analyzed.

3. Histopathological Examination

1. The resected tumor tissue was fixed in 10% neutral buffered formalin, routinely processed, and embedded in paraffin. Serial sections were cut at a thickness of 3–5 µm and then baked at 60 °C for 120 min.
2. After standard deparaffinization and rehydration with xylene and graded ethanol, sections were stained with hematoxylin-eosin (HE) and observed under a light microscope to evaluate histopathological morphological features.

4. Immunohistochemical Detection

Complete metadata for all primary antibodies (including clone number, manufacturer, catalog number, working dilution, detection system, and matched positive/negative tissue controls) is fully listed in the supplementary Table of Materials.

1. Immunohistochemical (IHC) staining was performed on serial paraffin sections for the markers CK-Pan, CK8/18, INSM1, Synaptophysin (Syn), CD56, Ki-67, and P53. Antigen retrieval was carried out using EDTA buffer (pH 8.0) in a pressure cooker; heated at 1600 W/210 °C until steam escaped, then maintained at 800 W/130 °C for 260 min.
2. After blocking endogenous peroxidase activity, all primary antibodies were incubated at room temperature for 30 min, followed by corresponding secondary antibody incubation. DAB chromogenic reaction was performed at room temperature for 1–10 min with continuous microscopic monitoring to control staining intensity.
3. All stained sections were independently evaluated by two senior pathologists to determine the positive expression location and positive rate of each biomarker.

5. Biosafety and waste disposal

1. All biospecimens, including patient urine samples and resected tumor tissues, were handled strictly in accordance with hospital biosafety management specifications. All experimental procedures were performed in a standardized pathological laboratory, with personal protective equipment worn throughout.
2. Biological waste such as residual urine specimens, paraffin debris, stained slides, and contaminated consumables was classified, sealed, and disposed of as medical biohazard waste. Chemical waste, including formalin fixative, xylene, ethanol, EDTA buffer, Wright-Giemsa staining solution, and DAB chromogenic solution, was collected separately in dedicated chemical waste containers to avoid environmental pollution.
3. All waste was uniformly recycled and processed by a qualified medical waste disposal institution, ensuring full compliance with biosafety and environmental protection regulations.

Results

Combined findings from imaging, exfoliative cytology of urine, histopathology, and immunohistochemistry enabled a definitive diagnosis of primary bladder large-cell neuroendocrine carcinoma (LCNEC). Urine cytology allowed noninvasive identification of malignant atypical cells, histopathology demonstrated characteristic neuroendocrine tumor morphology, and immunohistochemistry verified neuroendocrine differentiation and high proliferative activity. The diagnostic summary table integrates key results across all modalities ...

Discussion

Bladder cancer is one of the most common malignant tumors of the genitourinary system and frequently occurs in elderly males. Over the past three decades, the incidence of bladder cancer has gradually increased in China, exceeding the global average, and the mortality risk rises significantly with advancing age^3,4,5. Primary large cell neuroendocrine carcinoma (LCNEC) of the bladder is a rare high-grade subtype, first described ...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
64-slice spiral CT scanner (LightSpeed VCT)	GE Medical Systems, LLC	SFDA(I)20113300100; Serial No.: VCTC1001CT
Anti-CD56 antibody	AnBiPing	1216241224
Anti-CK-Pan antibody	AnBiPing	0714251118
Anti-CK8/18 antibody	AnBiPing	0827240911
Anti-INSM1 antibody	AnBiPing	1122241126
Anti-Ki-67 antibody	AnBiPing	0209260320
Anti-P53 antibody	AnBiPing	0105260121
Anti-Synaptophysin (Syn) antibody	AnBiPing	0819250901
DAB chromogenic kit	AnBiPing	T2603001
EDTA buffer	AnBiPing	1224251225
Flexible cystoscope	RUIDE	069772520300066
Hematoxylin-eosin (HE) staining kit	JinShengLai	2025102178, 2025061277
Neutral buffered formalin fixative	TongHe Bio	20260301
Resectoscope system	Zhuhai Simai Technology Co., Ltd.	1550085C
Wright-Giemsa staining solution	BASO Diagnostics Inc., Zhuhai	C240807
Xylene	FuYu Chemical	20260201F