Molecular characteristics of urothelial neoplasms in children and young adults: a subset of tumors from young patients harbors chromosomal abnormalities but not FGFR3 or TP53 gene mutations

Bladder Neoplasia in Pediatric Patients-A Single-Center Experience Including a Case Series

Objective: Bladder lesions like urothelial carcinoma are rare in the first two decades of life. A biopsy of the bladder or urinary cytological examination is seldom required. Gross painless hematuria is the most relevant clinical syndrome. Methods: A retrospective analysis of surgical pathology records collected between 1984 and 2014 at our institution was performed in a search for cases of urothelial neoplasms originating within the urinary bladder in pediatric patients. Diagnoses were confirmed based on pathologic examination using the 2004 World Health Organization (WHO) classification system. We selected keywords such as bladder neoplasia, bladder lesion, urothelial neoplasia, rhabdomyosarcoma, and children. In addition, we describe clinical presentation and diagnostic procedures as well as treatment and follow-up of two patients. A review of the literature was performed to analyze recommendations concerning diagnostic staging, treatment, and follow-up examinations as well as surveillance of urothelial tumors in the pediatric population. Results: Screening the pathology database of the Institute of Medical Genetics and Pathology of the University Hospital Basel between 1988 and 2014 yielded 287 samples involving the urinary bladder, 110 autopsies, 135 biopsies, and 42 cytology specimens. Of these, most samples originated from malformations and inflammation. Only five were tumors: two were urothelial tumors and three were rhabdomyosarcomas. The majority of specimens comprised resections of the diverticula or distal ureter. Our case reports include two patients with a urothelial tumor. Among the urothelial tumors, one was a papillary urothelial neoplasm of low malignant potential (PUNLMP). Painless hematuria was the directing clinical symptom. The tumor was investigated by FISH, and a 9p21 deletion was found. The second tumor-like lesion was a fibroepithelial polyp arising from the bladder neck. Conclusions: Bladder tumors in children are rare and mostly consist of urothelial and mesenchymal neoplasms. Rhabdomyosarcoma is the most common malignant bladder tumor in childhood. Similar to adult urothelial neoplasms, the loss of 9p21 is also implicated in urothelial neoplasms in childhood. Despite an increasing number of case reports and small series published within the last 2 decades, general treatment protocols including recommendations for staging, tumor markers, and follow-up examinations are still not yet available for this tumor entity in the pediatric population.

Impact of Age at Diagnosis of Bladder Cancer on Survival: A Surveillance, Epidemiology, and End Results-Based Study 2004-2015

BACKGROUND

An older age contributes to the development of bladder cancer. However, the relationship between advanced age at the diagnosis and prognosis of bladder cancer has been few reported. This study aimed to determine the effect of age on survival in bladder cancer with different subgroups.

METHODS

117,275 patients with bladder cancer, identified from the Surveillance, Epidemiology, and End Results database during 2004-2015 in America, were divided into 4 age groups (≤54, 55 to 64, 65 to 74, and ≥75 years). Multivariable Cox proportional-hazards model and competing risk model were conducted according to different age groups. Heat maps were plotted to show the impact of age on survival in subgroups classified by other clinicopathological variables. Moreover, restricted cubic spline was used to model the association between age and the risk of death.

RESULTS

Patients aged ≥75 years had shorter overall survival in comparison with those aged ≤54 years (hazard ratio [HR] = 5.36, 95% confidence interval [CI] = 5.13-5.59). Compared with patients aged ≤54 years, patients older than 75 years experienced a decreased rate of bladder cancer-specific survival (subdistribution HR = 2.15, 95% CI = 2.04-2.25). Heat maps also showed that older ages were associated with worse overall cumulative mortality and bladder cancer-specific cumulative mortality. Similarly, restricted cubic spline verified the impact of age on survival of bladder cancer.

CONCLUSIONS

Age at diagnosis of bladder cancer was found to be a significant predictor for the worse overall survival and bladder cancer-specific survival even in an era with more effective therapies. Exploring the reasons why older age contributes to poor outcomes for bladder cancer will be the focus of future research.

Molecular Pathologic Subtyping of Urothelial Bladder Carcinoma in Young Patients

Urothelial cancer is a heterogeneous disease with different molecular pathways that produce distinct molecular subtypes with specific characteristics and patient survival outcomes that require different therapeutic methods. Urothelial tumors in young patients appear to have distinct genetic features compared with their counterparts in older patients. Using a Lund subtype-specific immunohistochemistry panel, we performed molecular subtype profiling of an urothelial carcinoma case series (n = 49) in patients younger than 45 years of age. We demonstrate that the urothelial carcinoma in young patients tends to be of molecular urothelial-like A subtype (80%) and is associated with favorable, recurrent-free survival (P = .022). In the urothelial-like cluster, we identified a portion of patients (10%) with high-grade non-muscle-invasive cancers (so-called urothelial-like D type) that showed significantly higher levels of squamous differentiation and p16, E2F3, and ki67 expression in addition to aberrant expression of Ck20 and a trend toward lower recurrent-free survival (P = .057). Segregation of the cohort according to the decade of occurrence revealed that all tumors (n = 8) of patients younger than 30 years were clearly classified as urothelial-like A subtype. Statistically more aggressive molecular subtypes, such as urothelial-like D and basal/squamous-like (6%) subtypes, were identified in patients older than 30 years of age. Genomically unstable (2%) and mesenchymal-like (2%) subtypes were classified in the 40- to 44-year age group only. These data suggest that more aggressive molecular subtypes of bladder carcinoma appear and become more frequent with age. Further investigations are needed to validate this hypothesis.

Urothelial neoplasms in pediatric and young adult patients: A large single-center series

PURPOSE

Bladder cancer is the sixth most common cancer in the United States, but is exceedingly rare in young patients, leading to a lack of accepted standards for diagnosis, treatment, and surveillance. We review our institutional experience with bladder urothelial neoplasms in pediatric and young adult patients summarizing presentation, treatment, and outcomes.

METHODS

Surgical pathology records at our institution were searched for cases of urothelial neoplasms among patients ≤25 years of age treated between January 1997 and September 2016. Cases submitted exclusively for pathology review were excluded. Diagnoses were confirmed based on pathologic examination using the 2004 World Health Organization classification system.

RESULTS

Thirty-four patients were identified with a mean age of 21.1 years (range 8-25 years), and median follow-up was 25.1 months (1-187 months). The male to female ratio was 1.83:1. The most common presenting symptom was hematuria (n=26; 76%). Diagnoses were invasive urothelial carcinoma (n=3), noninvasive urothelial carcinoma (n=24), PUNLMP (n=6), and urothelial papilloma (n=1). Noninvasive lesions were resected by cystoscopy, after which 12% (n=4) experienced complications (grade II or greater). One patient with stage IV invasive disease at diagnosis died, and 2 patients developed recurrences. Of those with noninvasive carcinoma, 29% (n=7) required repeat cystoscopy soon after initial TURBT at outside institutions, and 17% (n=4) had tumors downgraded from high-grade to low-grade after pathology review.

CONCLUSION

Hematuria is the most common sign of bladder neoplasia in children and young adults and should be investigated by cystoscopy. The majority of urothelial neoplasms in these patients are noninvasive and can be successfully treated with transurethral resection.

LEVEL OF EVIDENCE

Level IV (Retrospective study with no comparison group).

Immunohistochemical and molecular characterizations in urothelial carcinoma of bladder in patients less than 45 years

Bladder tumours in early-onset patients are rare and seem to exhibit unique clinicopathological features. Only few studies have investigated somatic alterations in this specific age of onset group and evidence is accumulating of a distinct molecular behaviour of early-onset bladder tumours. We collected the largest cohort of early-onset tumours of patients 45 years old or younger and aimed to test genomic alterations typically found in bladder cancer. Tumours of 118 early-onset patients were compared with a consecutive group of 113 cases. Immunohistochemistry of TP53, CK20 and Ki-67 was carried out. Molecular analysis was conducted to test for loss of heterozygosity of chromosome 9 and 17, as well as TP53 and FGFR3 mutations. Fisher´s exact and chi-squared test were appropriately used. No differences in grade/stage characteristics were observed. Overexpressed TP53 was differentially distributed between the two groups. TP53 nuclear accumulation was significantly more frequent in early-onset papillomas, PUNLMPs and pTa low-grade tumours compared to the consecutive cohort (p=0.005). Moreover, chromosome 9 deletions (29.5% vs. 44.6%) and FGFR3 mutations (34.5% vs. 63.7%) were less often detected in early-onset patients (p=0.05 and p<0.0001). By comparing the largest cohort of early-onset bladder cancer patients with an unselected group, we demonstrated that the typical molecular features are not independent of age at diagnosis. Our study supports the hypothesis of a distinct biological behaviour in early-onset tumours.

[Urothelial tumors in children]

Urothelial tumors are very rare in children (to date, only about 150 cases have been reported worlwide). Only 20% occur before the age of ten. The aim of this study is to specify the clinicopathologic features of urothelial tumor in young patients, which require a slightly different approach to treatment. On the basis of the WHO/ISUP (World Health Organisation/International Society of Urological Pathology) consensus classification report, these lesions are usually low-grade lesions, non invasive, and rarely recurrent. The sex ratio is three boys to one girl. These tumors are located preferentially in the low urinary tract, especially in the bladder. The main symptom is the macroscopic hematuria, which requires ultrasound examination in all cases. Cystoscopy is indicated in case of lesion of the bladder wall, or in case of persistent or recurrent hematuria, to obtain definitive diagnosis and biopsies. The tumors are mainly located on the posterior or lateral bladder wall above the trigone or near the ureteral orifices. Treatment is based on the transurethral resection of the lesion. The subsequent monitoring is sparsely codified, due to the exceptional occurrence of these tumors in the paediatric age group. These patients are likely to have better outcome than older patients, but it is due to the predominance of noninvasive papillary urothelial tumors. Tumor recurrences are not uncommon. In case of invasive, high-grade urothelial carcinomas, metastases or even lethal outcome may occur in rare cases.

TERT Core Promotor Mutations in Early-Onset Bladder Cancer

Activating mutations in the core promoter of the TERT gene have been described in many different tumor entities. In vitro models showed a two- to fourfold increase in transcriptional activity of the TERT promoter through creation of a consensus binding motif for Ets/TCF transcription factors caused by these mutations. TERT core promoter mutations are the most common mutations in bladder cancer with a frequency between 55.6% and 82.8% described so far, and are independent of stage and grade. Since limited data on molecular alterations of early-onset bladder tumors exists, we assessed the frequency of TERT core promoter mutations in early-onset bladder cancer. Two cohorts of bladder tumors (early-onset patient group; n=144 (age of onset of disease ≤45 years); unselected, consecutive group; n=125) were examined for TERT core promoter mutations. After microdissection and extraction of DNA the corresponding hotspot regions in the TERT core promoter were examined by Sanger-sequencing or a SNaPshot approach. A significantly lower frequency of TERT core promoter mutations was found in tumors from the early-onset cohort compared to the consecutive cohort (57.6% vs. 84.8%, p<0.001). Among the early-onset cohort cases younger than the cohort's median age of 39 years at disease onset showed a significantly reduced number of TERT promoter mutations (31/67, 46,3%) than cases aged between 39 and 45 years (52/77, 67.5%; p=0.012). This association was not found in the consecutive cases. Mutation status was independent of tumor stage and grade. We conclude that in tumors from early-onset bladder cancer patients TERT core promoter mutations are not as frequent as in bladder tumors from consecutive cases, but seem to play an important role there as well. In patients below 39 years of age TERT core promoter mutations are a more infrequent event, suggesting different mechanisms of tumorigenesis in these young patients.

H-RAS mutation is a key molecular feature of pediatric urothelial bladder cancer. A detailed report of three cases

INTRODUCTION

Urothelial carcinoma (UC) of the bladder is a rare entity in the pediatric population, with an incidence of less than 0.4% in patients younger than 20 years. These patients overwhelmingly present with non-muscle-invasive low-grade disease and an indolent behavior.

OBJECTIVE

The aim was to determine the source of the different natural history between pediatric population and adults; we hypothesized that pediatric bladder cancer may stem from different molecular pathways. Our objective with this descriptive case series was to study the main genes involved in pediatric urothelial bladder carcinoma using immunohistochemical (IHC) and mutational analysis. By studying the genetic alterations and immunophenotype of the most commonly altered genes in bladder urothelial cancer in three pediatric tumors we could gain better understanding of the molecular pathogenesis in this rare disease.

STUDY DESIGN

Formalin-fixed paraffin-embedded (FFPE) tissue slides of urothelial bladder tumors from three pediatric patients were retrospectively identified at Columbia University pathology archives (1990-2011) and re-evaluated. FGFR3, H-RAS, and PI3K hotspots mutational analyses were conducted by polymerase chain reaction amplification and Sanger sequencing from the FFPE tissue blocks. IHC analysis was conducted using antibodies against p53, PTEN, RB, EGFR, and HER2. Proliferative rate was assessed by Ki-67 expression.

RESULTS

Two patients had low-grade Ta disease, whereas the other tumor was classified as a papillary urothelial neoplasm of low malignant potential. None of the lesions recurred. Notably, all specimens showed H-RAS G12V mutation, whereas they were characterized by wild-type FGFR3 and PI3K. Nuclear p53 was not detected, whereas PTEN and RB expression were maintained. EGFR was expressed in the three cases and HER2 was negative. The proliferation rate was very low in all cases.

DISCUSSION

It is difficult to draw strong conclusions from the study of three tumors treated at the same institution and from the same referral population, and a multicentric study should be performed to confirm these preliminary results. However, we propose that H-RAS mutation analysis could be performed on urothelial bladder tumors of pediatric patients. The knowledge in the molecular basis of urothelial bladder tumors in children opens a promising field which could lead us to establish different guidelines for surveillance and follow-up of pediatric urothelial bladder cancer patients.

CONCLUSION

Pediatric tumors are characterized by a consistent H-RAS mutation status, whereas FGFR3 and p53 pathways are not involved in this tumor initiation. These results may explain the few recurrences seen in this population.

Genetics of Bladder Malignant Tumors in Childhood

Bladder masses are represented by either benign or malignant entities. Malignant bladder tumors are frequent causes of disease and death in western countries. However, in children they are less common. Additionally, different features are found in childhood, in which non epithelial tumors are more common than epithelial ones. Rhabdomyosarcoma is the most common pediatric bladder tumor, but many other types of lesions may be found, such as malignant rhabdoid tumor (MRT), inflammatory myofibroblastic tumor and neuroblastoma. Other rarer tumors described in literature include urothelial carcinoma and other epithelial neoplasms. Rhabdomyosarcoma is associated to a variety of genetic syndromes and many genes are involved in tumor development. PAX3-FKHR and PAX7-FKHR (P-F) fusion state has important implications in the pathogenesis and biology of RMS, and different genes alterations are involved in the pathogenesis of P-F negative and embryonal RMS, which are the subsets of tumors most frequently affecting the bladder. These genes include p53, MEF2, MYOG, Ptch1, Gli1, Gli3, Myf5, MyoD1, NF1, NRAS, KRAS, HRAS, FGFR4, PIK3CA, CTNNB1, FBXW7, IGF1R, PDGFRA, ERBB2/4, MET, BCOR. Malignant rhabdoid tumor (MRT) usually shows SMARCB1/INI1 alterations. Anaplastic lymphoma kinase (ALK) gene translocations are the most frequently associated alterations in inflammatory myofibroblastic tumor (IMT). Few genes alterations in urothelial neoplasms have been reported in the paediatric population, which are mainly related to deletion of p16/lnk4, overexpression of CK20 and overexpression of p53. Here, we reviewed available literature to identify genes associated to bladder malignancies in children and discussed their possible relationships with these tumors.