Primary renal well-differentiated neuroendocrine tumors: report of six cases with an emphasis on the Ki-67 index and mitosis

Basic science and translational implications of current knowledge on neuroendocrine tumors

Neuroendocrine tumors (NETs) are a diverse group of malignancies that can occur in various organs, with a notable prevalence in the lungs and gastrointestinal tract, which are the focus of this Review. Although NETs are rare in individual organs, their incidence has increased over recent decades, highlighting the urgent need for current classification systems to evolve by incorporating recent advances in the understanding of NET biology. Several omics studies have revealed molecular subtypes, which, when integrated into existing classification frameworks, may provide more clinically relevant insights for patients with NETs. This Review examines recent progress in elucidating the biology of NETs, with a particular emphasis on the tumor microenvironment and cells of origin. The existence of different cells of origin, which may contribute to distinct molecular groups, along with profiles of immune infiltration - despite being generally low - could explain the emergence of more aggressive cases and the potential for metastatic progression. Given the molecular heterogeneity of NETs and the diversity of their microenvironments and different cells of origin, there is an urgent need to develop morphomolecular classification systems. Such systems would make it possible to better characterize tumor progression, identify new therapeutic targets, and, ultimately, guide the development of personalized therapies.

Primary Renal Well-Differentiated Neuroendocrine Tumor: A Clinicopathologic and Immunohistochemical Analysis of a Case Series With Emphasis on Potential Diagnostic Pitfalls

Introduction. Primary renal well-differentiated neuroendocrine tumor may present a unique diagnostic and therapeutic challenge. In this retrospective study, we offered insights derived from our clinical experience. Methods. A search of our institutional database (1998-2023) was performed to identify primary renal well-differentiated neuroendocrine tumors, followed by comprehensive clinical, histopathological and immunohistochemical analysis, with emphasis on potential diagnostic pitfalls. Results. Five primary renal well-differentiated neuroendocrine tumors were identified, all of which exhibited a combination of nested, trabecular and tubular growth patterns and renal parenchymal infiltration. Two tumors invaded into the renal sinus. The expression of commonly-used neuroendocrine markers was detected in 5 tumors and PAX8 immunostain was negative in all tumors. During a median follow-up of 119 months (range 12-142 months), one patient received adjuvant chemotherapy due to regional lymph node metastasis at the time of diagnosis. The patient was found to haveliver metastasis at 15 months after the surgery by imaging. This tumor harbored BRAF c.1/99T>A, p.V600E and CDKN2A c.35delC, p.S12fs variants. Liver metastasis was identified in another patient 142 months after his initial presentation. No local recurrence or distant metastasis was detected in other patients. Conclustions. Our experience demonstrates that primary renal well-differentiated neuroendocrine tumors may exhibit indolent behavior, even tumors with local invasion. Most patients were managed with surgical resection alone. In daily practice, they may be misdiagnosed as renal cell carcinomas, especially in biopsy specimens, due to their rarity. Our study expands the clinicopathologic characteristics and immunohistochemical features of this rare entity to raise awareness, with emphasis on potential diagnostic pitfalls.

Atypical carcinoid of the primary kidney with retroperitoneal metastasis 15 years later: A case report and literature review

Primary renal neuroendocrine tumors (NETs) are extremely rare among renal malignancies. According to pathological manifestations, carcinoid can be divided into four types: typical carcinoid, atypical carcinoid, large cell and small cell neuroendocrine carcinoma. Primary or secondary retroperitoneal carcinoid is even rarer than renal carcinoid. This article reports a patient with renal carcinoid complicated with retroperitoneal metastasis, who developed retroperitoneal metastasis 15 years after radical nephrectomy. Through the analysis of this case and the combination of the existing published literature, it is aimed to provide valuable references for clinicians in treating patients with renal carcinoid or with metastasis.

A Case Report of Carcinoid With Teratoma Arising From the Renal Hilum

Teratoma is a germ cell tumor composed of 2 or 3 germ cell layers, and it can occur in various parts of the human body. However, teratomas of the renal hilum are particularly rare, and those complicated by carcinoids are even more uncommon. Herein, we report the example of an asymptomatic 49-year-old woman in whom a tumor in the right renal hilum was unexpectedly discovered on imaging. Histological examination revealed a carcinoid tumor arising from a simple cyst composed of teratomatous tissue. Although the tumor was located in the renal hilum and touched the renal parenchyma, it appeared independent of the kidney and urinary tract. This report highlights the rare occurrence of teratomas with carcinoids and provides insights into their origins.

Therapeutic Response to PRRNT in a Rare Case of Metastatic Renal Neuroendocrine Carcinoma

Neuroendocrine tumors (NETs) are a rare spectrum of neoplasms that are characterized by neuroendocrine and neural differentiation. The treatment can be challenging in view of the heterogeneity in differentiation and behavior. Primary renal origin NETs are rare and only a few cases have been reported in the literature. There is limited knowledge on their presentation and response to various lines of treatment. We report a case of a patient with a metastatic renal NET from a rare histological subtype of large cell neuroendocrine carcinoma, known to cause aggressive disease with poor prognosis. A multimodality treatment approach was followed. In spite of surgical management and second-line chemotherapy, the disease progressed. The patient subsequently received peptide receptor radionuclide therapy (PRRNT) using lutetium-177 DOTATATE, following which the patient demonstrated a remarkable clinical and radiological response and is stable to date. In a rare tumor with poor prognosis, the relevance of theranostics and the efficacy of targeted therapies like PRRNT are noteworthy.

Renal neuroendocrine tumors: clinical and molecular pathology with an emphasis on frequent association with ectopic Cushing syndrome

Renal neuroendocrine tumors (RenNETs) are rare malignancies with largely unknown biology, hormone expression, and genetic abnormalities. This study aims to improve our understanding of the RenNETs with emphasis of functional, hormonal, and genetic features. Surgically resected RenNETs (N = 13) were retrieved, and immunohistochemistry and next-generation sequencing (NGS) were performed in all cases. In addition, all published RenNETs were systematically reviewed. Our cohort (4 men and 9 women, mean age 42, mean tumor size 7.6 cm) included 2 patients with Cushing syndrome (CS). WHO grade (23% G1, 54% G2, and 23% G3) and tumor progression did not correlate. CS-associated RenNETs (CS-RenNETs) showed a solid and eosinophilic histology and stained for ACTH, while the remaining non-functioning tumors had a trabecular pattern and expressed variably hormones somatostatin (91%), pancreatic polypeptide (63%), glucagon (54%), and serotonin (18%). The transcription factors ISL1 and SATB2 were expressed in all non-functioning, but not in CS-RenNETs. NGS revealed no pathogenic alterations or gene fusions. In the literature review (N = 194), 15 (8%) of the patients had hormonal syndromes, in which CS being the most frequent (7/15). Large tumor size and presence of metastasis were associated with shorter patients' survival (p < 0.01). RenNETs present as large tumors with metastases. CS-RenNETs differ through ACTH production and solid-eosinophilic histology from the non-functioning trabecular RenNETs that produce pancreas-related hormones and express ISL1 and SATB2. MEN1 or DAXX/ARTX abnormalities and fusion genes are not detected in RenNETs, indicating a distinct yet unknown molecular pathogenesis.

Primary Renal Well-Differentiated Neuroendocrine Tumors: Analyis of Six Cases from a Tertiary Care Center in North India with Review of Literature

Well-differentiated renal neuroendocrine tumors are rare tumors. As their biologic behavior is not fully known, there is a need to know more about these cases. We performed a retrospective chart review of all the cases diagnosed with renal neuroendocrine tumors from January 2016 to December 2020 (five years) in order to understand their clinical features, morphological characteristics and outcome. We included six cases with mean age of 46.2 years (4 males) in our study. All patients underwent radical nephrectomy. Histologically all showed tumor disposed in nests and trabeculae and majority of the tumors belonged to well-differentiated neuroendocrine tumor Grade 1 (WHO criteria of gastoroenteropancreatic neuroendocrine neoplasms). Lymph node metastasis was seen in two cases at the time of clinical presentation. All the tumors were diffusely positive for neuroendocrine tumor markers (synaptophysin, chromogranin, NSE, CD56). Follow-up data was available in all cases with an average follow-up of two years and neither has shown evidence of metastasis or relapse till last follow-up. Role of morphological patterns and immunohistochemical markers is highlighted with the importance of including Ki-67 index in grading them to better understand their outcome.

Primary neuroendocrine neoplasms of the kidney: a case report and literature review

Primary kidney neuroendocrine tumors (NETs) are rare renal malignancies. However, detecting and monitoring neuroendocrine neoplasms remains challenging because of their nonspecific nature. We herein present a case involving a 53-year-old woman who experienced episodes of intermittent abdominal pain, dizziness, and nausea for a period of 5 days. Computed tomography urography revealed a small (approximately 19- × 16-mm) nodular shadow in the left kidney. The nodular shadow exhibited slightly lower density than the surrounding tissue as well as enhancement, with a portion protruding into the renal sinus region. Histological and immunohistochemical analyses of the biopsy specimen from the mass indicated a well-differentiated NET. After analysis of this case, we performed a literature review and herein discuss various techniques for imaging and pathological diagnosis of renal NETs. Additionally, we provide insights into the treatment options and prognosis for affected patients. By combining this case study with the existing published literature, we aim to offer a valuable reference for clinicians treatment patients diagnosed with renal NETs.

[New WHO classification 2022: urinary bladder cancer]

The new World Health Organization (WHO) classification of urogenital tumors is still primarily based on anatomic location, but is also a hierarchical taxonomic classification without separate chapters for tumors of the upper urinary tract and the urethra. It clarifies aspects regarding grading and noninvasive entities. It consolidates the use of the Paris system for urinary cytology as well as various subtypes/special types of neoplasms, and incorporates general concepts of the 5th edition of the WHO blue book. In addition to mesenchymal tumors, well-differentiated neuroendocrine tumors and neuroendocrine carcinomas are addressed in separate chapters. Papillary non-invasive low- and high-grade carcinomas and carcinoma in situ remain, while dysplasia and urothelial proliferation of unknown malignant potential (UPUMP) are no longer treated as separate entities. Former variants of urothelial carcinoma are now called subtypes and aberrant differentiation and special types are more precisely defined.

Diagnostic, Prognostic, and Predictive Role of Ki67 Proliferative Index in Neuroendocrine and Endocrine Neoplasms: Past, Present, and Future

The introduction of Ki67 immunohistochemistry in the work-up of neuroendocrine neoplasms (NENs) has opened a new approach for their diagnosis and prognostic evaluation. Since the first demonstration of the prognostic role of Ki67 proliferative index in pancreatic NENs in 1996, several studies have been performed to explore its prognostic, diagnostic, and predictive role in other neuroendocrine and endocrine neoplasms. A large amount of information is now available and published results globally indicate that Ki67 proliferative index is useful to this scope, although some differences exist in relation to tumor site and type. In gut and pancreatic NENs, the Ki67 proliferative index has a well-documented and accepted diagnostic and prognostic role and its evaluation is mandatory in their diagnostic work-up. In the lung, the Ki67 index is recommended for the diagnosis of NENs on biopsy specimens, but its diagnostic role in surgical specimens still remains to be officially accepted, although its prognostic role is now well documented. In other organs, such as the pituitary, parathyroid, thyroid (follicular cell-derived neoplasms), and adrenal medulla, the Ki67 index does not play a diagnostic role and its prognostic value still remains a controversial issue. In medullary thyroid carcinoma, the Ki67 labelling index is used to define the tumor grade together with other morphological parameters, while in the adrenal cortical carcinoma, it is useful to select patients to treated with mitotane therapy. In the present review, the most important information on the diagnostic, prognostic, and predictive role of Ki67 proliferative index is presented discussing the current knowledge. In addition, technical issues related to the evaluation of Ki67 proliferative index and the future perspectives of the application of Ki67 immunostaining in endocrine and neuroendocrine neoplasms is discussed.

A Rare Case of a Large Primary Renal Neuroendocrine Tumour: A Case Report and Brief Review of Literature

Primary renal neuroendocrine tumours are very rare clinical entities, and as such, relatively little is known about their clinical progression. Here, we outline the case of a young female patient presenting with abdominal pain and a large 14 cm right renal mass. Initial radiological studies demonstrated localised disease, but during surgical resection, widespread liver metastasis was identified. Histological analysis revealed a grade 2, well-differentiated neuroendocrine tumour pT3a. Whilst surgical resection remains the gold standard for localised disease, further work is required to understand the pathogenesis, prognostic indicators and treatment following metastatic spread. The poor prognosis seen in primary renal neuroendocrine neoplasia highlights the importance of further directed research in this area.

Single institutional experience on primary neuroendocrine neoplasms of the kidney: a rare distinct entity

Primary pure renal neuroendocrine neoplasms (R-NENs) are a distinct and rare entity. Not much is known about the histopathology and biologic behavior of these tumors. We attempted to review the clinicopathologic aspects of these neoplasms encountered at our institution. We performed a retrospective chart review to identify primary pure (not admixed with any other tumor component) R-NENs from institutional Cancer Registry database. Pathologic review of the diagnostic archival slides was done for detailed assessment of the histologic features. R-NENs were classified according to the current WHO system for gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs). Eight pure R-NEN cases were identified, all unifocal, and most (6/8) involved the right kidney. Three patients had poorly differentiated neuroendocrine carcinoma (NEC), and five had well-differentiated neuroendocrine tumor (NET). All tumors were located near the renal hilum, stained diffusely with synaptophysin, variably with chromogranin, and were negative for renal site-specific marker PAX8 or for markers of renal cell carcinoma. We identified two distinct patterns of growth: one of sheets with interspersed rosettes and the other of large nests with low proliferative crowded centers and peripheral cells with higher proliferation and prominent palisading. Based on Ki-67 proliferative index, the tumors were classifiable into WHO grade 1 or grade 2 (based on GEP-NEN). All three NECs characteristically showed cytologic features intermediate between classic large and small cell type. This is the first comprehensive clinicopathologic study involving the rare group of R-NEN. Classifying and grading them according to the GEP-NEN system is of prognostic significance.

Primary Renal Carcinoid Tumor: Report of Two Cases

INTRODUCTION

Primary renal carcinoid tumors are a rare subset of neuroendocrine tumors arising in the kidneys. Although carcinoid syndrome has occasionally been described, most patients are asymptomatic at presentation.

CASE PRESENTATIONS

We present 2 cases of primary renal carcinoid tumor and describe the workup, immunohistochemical analysis, treatment, and surveillance of each female patient. The first patient was found to have a renal mass on imaging during a workup of chronic abdominal pain and subsequently underwent a robotic radical nephrectomy. The second patient was found to have an incidental renal mass on imaging and subsequently underwent renal biopsy, followed by robot-assisted laparoscopic partial nephrectomy. In both cases, a gallium dotatate Ga 68-enhanced positron emission tomography/computed tomography scan was used to further assess disease burden.

DISCUSSION

This report describes 2 cases of primary renal carcinoid tumor with unique presentations and management in our regional health care system. Because primary renal carcinoid tumors are quite uncommon, there are no clear established guidelines on preoperative imaging or posttreatment surveillance in patients with these tumors. There remains a large amount of variability in the diagnosis, workup, immunohistochemical analysis, treatment, and surveillance of patients with primary renal carcinoid tumors. As we learn more about this disease, we hope to optimize patient outcomes and standardize pretreatment workup and posttreatment surveillance.

Renal Neuroendocrine Neoplasms: A Single-center Experience

BACKGROUND

Primary neuroendocrine neoplasms (NENs) of the kidney are exceedingly rare malignancies and the available literature is very limited. The natural history and response to treatments is not well characterized. We aimed to describe the presenting features, demographics, tumor characteristics, and treatment outcomes of patients with renal NENs.

PATIENTS AND METHODS

We performed a retrospective analysis of all Mayo Clinic patient records with a tissue diagnosis of a primary renal NEN. Baseline patient and surgical pathologic features and treatment modalities were collected. Time to recurrence after resection and overall survival (OS) were estimated using with survival analysis. Surveillance, Epidemiology, and End Results data were used to estimate the population-wide incidence and OS.

RESULTS

A total of 17 patients were included in the present study, with a median follow-up of 62.8 months. Distant metastasis was present in 29% at diagnosis, with 76% experiencing distant metastasis at any point; 24% had a horseshoe kidney. Of the 17 patients, 14 had undergone surgical resection with no evidence of disease postoperatively. Ten of these patients had documented recurrence. The median time to recurrence was 18 months (95% confidence interval, 9-46 months). Only 1 of the 10 patients showed a radiographic response to systemic therapy. Of 9 patients, 4 had stable disease with somatostatin analogs. The median OS was 143 months (95% confidence interval, 50-143 months).

CONCLUSIONS

Renal NENs are rare malignancies affecting mostly middle-age patients, with distant metastasis being common. Approximately one half of patients experience stable disease with somatostatin analogs. The OS usually exceeds 5 years.