Correlation of Ki-67 and p53 with the new World Health Organization/International Society of Urological Pathology Classification System for Urothelial Neoplasia

OBJECTIVE: The present study examines p53 and Ki-67 staining patterns of the diagnostic entities included within the new World Health Organization/International Society of Urological Pathology (WHO/ISUP) classification of urothelial neoplasms. DESIGN: We retrospectively studied 151 bladder biopsies from 81 patients with the following neoplasms: normal urothelium (n = 34 biopsies); low-grade intraurothelial neoplasia (LGIUN; n = 19); high-grade intraurothelial neoplasia (HGIUN; n = 20); papillary hyperplasia (n = 4); papilloma (n = 3); papillary neoplasm of low malignant potential (LMP; n = 12); low-grade papillary carcinoma (n = 28); and high-grade papillary carcinoma (n = 31). Sections were labeled immunohistochemically with antibodies to p53 and Ki-67 (MIB-1). Two hundred cells from each lesion were visually counted, and the percentage of positive cells was tabulated without knowledge of the WHO/ISUP diagnosis. RESULTS: In flat lesions, p53 positivity was of limited diagnostic utility; the marker was present in 6 of 34 benign biopsies, 6 of 19 LGIUNs, and 10 of 20 HGIUNs. In one case in which HGIUN was present elsewhere in the bladder, 29% of the benign urothelial cells were p53 positive. In papillary lesions, p53 positivity was not seen in 4 of 4 cases of papillary hyperplasia, 3 of 3 papillomas, and 8 of 12 LMP tumors. In contrast, p53 was detected in 18 of 28 low-grade and 26 of 31 high-grade papillary urothelial carcinomas. A p53 labeling index (LI) greater than 30% was only seen in HGIUNs and high-grade papillary carcinomas. In flat lesions, an increased Ki-67 LI separated out benign urothelium (mean LI, 0.62%) from dysplasia (mean LI, 3.3%) and HGIUN (mean LI, 11.6%). In papillary lesions, Ki-67 positivity was as follows: papillary hyperplasia (mean LI, 1.1%); papilloma (mean LI, 4.3%); LMP tumors (mean LI, 2.5%), low-grade papillary carcinoma (mean LI, 7.3%); and high-grade carcinoma (mean LI, 15.7%). A Ki-67 LI greater than 10% was seen only in low- and high-grade papillary carcinomas, HGIUN, and single cases of LGIUN and papillary neoplasm of LMP. CONCLUSIONS: An increased proliferative index as demonstrated by immunohistochemical staining for Ki-67 (MIB-1) is most often seen in papillary carcinoma and HGIUN. Marked p53 positivity is also characteristic of carcinoma but may be seen in benign-appearing urothelium, suggesting a "field effect" with occult molecular aberration.     

Genomic aberrations are rare in urothelial neoplasms of patients 19 years or younger

Urothelial neoplasms in patients 19 years of age or younger are rare, and the data regarding clinical outcome are conflicting. Molecular data are not available. Urothelial tumours from 14 patients aged 4 to 19 years were analysed, including FGFR3 and TP53 mutation screening, comparative genomic hybridization (CGH), UroVysion FISH analysis, polymerase chain reaction for human papillomavirus (HPV), microsatellite analysis using the NIH consensus panel for detection of microsatellite instability (MSI) and six markers for loss of heterozygosity on chromosome arms 9p, 9q, and 17p and immunohistochemistry for TP53, Ki-67, CK20 and the mismatch repair proteins (MRPs) hMSH2, hMLH1, and hMSH6. Based on the 2004 WHO classification, one urothelial papilloma, seven papillary urothelial neoplasms of low malignant potential (PUNLMPs), five low-grade, and one high-grade papillary urothelial carcinoma were included. No multifocal tumours were found and recurrence was seen in only one patient with a urothelial papilloma. All patients were alive with no evidence of disease at a median follow-up of 3.0 years. We found no mutations in FGFR3, deletions of chromosome arms 9p, 9q or 17p, MSI or MRP loss, or HPV positivity in any of the patients. Three cases showed chromosome alterations in CGH analyses, urothelial dedifferentiation with CK20 overexpression, or aneuploidy, and one TP53 mutation with TP53 overexpression was found. Urothelial neoplasms in people younger than 20 years are predominantly low grade and are associated with a favourable clinical outcome. Genetic alterations frequently seen in older adults are extremely rare in young patients. Urothelial neoplasms in children and young adults appear to be biologically distinct and lack genetic instability in most cases.     

Urothelial (transitional cell) papilloma of the urinary bladder: a clinicopathologic study of 26 cases.

The existence of a papillary lesion of the urinary bladder with a benign clinical course and recognizable morphologic features that merit the benign categorization "papilloma" has been controversial. The clinical aspects and histologic features of these lesions remain to be fully elucidated. We have studied the clinicopathologic features of 26 patients with urothelial papillomas and correlated them with outcome. Papillomas occurred in two distinct clinical settings: (1) de novo neoplasms (23/26) or (2) those occurring in patients with a known clinical history of bladder cancer ("secondary" papillomas; 3/26). Follow-up information was available in 14/23 of the de novo cases (mean = 39 mo) and in 3/3 secondary cases (mean = 24 mo). Patients with de novo papillomas had a mean age of 46 years; 16 were male and 7 were female. Twelve of 14 had a benign clinical course with no recurrences; 1 developed a recurrent papilloma at 3 years, and 1 developed a pT3a high-grade papillary urothelial carcinoma at 4 years. Patients with secondary papillomas had a mean age of 66 years; two were male and one was a female. One of these patients developed two additional recurrences, and two patients had no new recurrences. Morphologically, the papillary architecture ranged from a common simple, nonhierarchical arrangement to, infrequently, more complex anastomosing papillae with budding. The individual papillae ranged from small (most common), with scant stroma and slender fibrovascular cores, to large, with marked stromal edema and/or cystitis cystica-like urothelial invaginations. Common to all was a lining of normal-appearing urothelium without hyperplasia, maintenance of normal polarity, and frequent prominence of the umbrella cell layer. Overall, no patient with a diagnosis of papilloma died of disease; only one patient with a de novo lesion (7.0%) had a recurrent papilloma, and 1/14 (7.0%) progressed to a higher grade and stage of disease, although this patient was on immunosuppressive therapy secondary to a renal transplant. De novo urothelial papillomas occur in younger patients and usually have a benign course. Urothelial papillomas are histologically and probably biologically distinctive tumors and merit distinction from other higher risk papillary neoplasms of the urinary bladder.     

Somatic mutation of fibroblast growth factor receptor-3 (FGFR3) defines a distinct morphological subtype of high-grade urothelial carcinoma

FGFR3 mutations are common in low-grade urothelial carcinoma and represent a potential therapeutic target in this disease. Their incidence and functional role in high-grade urothelial carcinoma (HGUC), which displays an increased propensity for recurrence and muscularis propria invasion, is less well defined. We developed a mass spectrometry-based genotyping assay to define the incidence of FGFR3 mutations in a large clinically annotated set of urothelial carcinomas. FGFR3 mutations were found in 17% of HGUC versus 84% of low-grade lesions. Retrospective pathological review of the class of FGFR3 mutant HGUC revealed unique histological features, characterized by a bulky, exophytic component with branching papillary architecture as well as irregular nuclei with a koilocytoid appearance. The predictive value of this histological appearance was confirmed using a prospective set of 49 additional HGUCs. Prospective histological review was able to correctly predict for the presence of an FGFR3 mutation in 13/24 HGUC specimens that exhibited the distinct morphology (54%). All 25 specimens lacking the defined histological features were FGFR3 wild-type for a negative predictive value of 100%. Macrodissection of individual tumours confirmed the presence of the FGFR3 mutant allele in non-invasive and invasive, low and high-grade regions of individual tumours and in the lymph node metastases of patients whose tumours possessed the characteristic morphological signature, suggesting that FGFR3 mutations are not restricted to the more clinically indolent regions of HGUCs. These data suggest that histological screening of HGUCs followed by confirmatory genotyping can be used to enrich for the population of HGUCs most likely to harbour activating mutations in the FGFR-3 receptor tyrosine kinase. Histological review could thus aid in the development of targeted inhibitors of FGFR-3 by facilitating the identification of the subset of patients most likely to harbour activating mutations in the FGFR3 gene.     

Prognostic significance of atypical papillary urothelial hyperplasia

Typical papillary hyperplasia, a recently recognized precursor lesion to low-grade papillary urothelial neoplasms, consists of undulating folds of cytologically benign urothelium. Well-developed, branching fibrovascular cores of a papillary neoplasm are not evident. We have noted lesions with the architectural pattern of papillary hyperplasia; however, the overlying urothelium demonstrated varying degrees of cytologic atypia. We identified 15 cases of atypical papillary hyperplasia (13 males, 2 females, age 55 to 92) with overlying urothelium showing cytologic atypia. Of these cases, 8 (53%) were received in consultation. Of the 15 cases, 8 exhibited overlying flat carcinoma in situ (CIS), 4 had overlying dysplasia, and 3 were transitional between papillary hyperplasia with atypia and the earliest lesions of papillary neoplasia. Of these cases, 5 patients had multiple specimens with atypical papillary hyperplasia (range, 2 to 8) over time. Concurrent to the diagnosis of atypical papillary hyperplasia, there were 25 different urothelial lesions: CIS (n = 11), papilloma (n = 1), papillary neoplasm of low malignant potential with CIS (n = 1), high-grade papillary urothelial carcinoma (n = 10; 3 with CIS), small-cell carcinoma (n = 1), and infiltrating urothelial carcinoma (n = 1). Of 11 patients with known prior history, 2 had 12 prior urothelial neoplasms (9 low-grade papillary neoplasms, 2 papillary urothelial neoplasms of low malignant potential, and 1 high-grade papillary cancer). Of 10 patients with atypical papillary hyperplasia and a minimum of 1 year of follow-up, 9 had 19 recurrences: CIS (n = 4), papilloma (n = 1), papillary neoplasm of low malignant potential (n = 1), infiltrating urothelial carcinoma (n = 3; 1 with CIS), and high-grade papillary urothelial carcinoma (n = 10; 5 with invasion and 2 with CIS). Whether the papillary hyperplasia had overlying CIS or dysplasia did not affect the correlation with urothelial neoplasms. Immunohistochemical analysis of p53 and Ki-67 expression in 8 cases demonstrated overexpression of p53 (n = 2; 1 with overlying dysplasia and 1 with overlying CIS), and Ki-67 (n = 5; 2 with overlying dysplasia and 3 with overlying CIS). Taken together, these results suggest that atypical papillary hyperplasia is most frequently associated with CIS and high-grade papillary cancer. In some cases, CIS or dysplasia may evolve into atypical papillary hyperplasia, with further progression to high-grade papillary cancer. This process may be analogous to papillary hyperplasia without cytologic atypia progressing to low-grade papillary urothelial neoplasms.     

Impact of the 1998 World Health Organization/International Society of Urological Pathology classification system for urothelial neoplasms of the kidney.

The classification of urothelial neoplasms of the kidney traditionally has been similar to that of urinary bladder tumors. Several years ago, the classification of papillary urothelial neoplasms was revised. The current study focuses on the application of the 1998 World Health Organization (WHO)/International Society of Urological Pathology classification system to 102 renal pelvic urothelial neoplasms and compares it to the 1973 WHO classification scheme. In this study, all tumors were classified as urothelial carcinomas, and the majority (85%) were papillary. Most patients with papillary tumors presented with 'superficial' disease (< or = pT1). With the 1998 system, most papillary carcinomas were high grade, and were more often invasive as compared to low-grade tumors. Only 34% were low-grade papillary tumors and, of these, most (93%) were noninvasive. With the 1973 system, most papillary tumors were grade 2 or 3, with invasion more common in grade 3 tumors. By 1973 criteria, grade 2 tumors were a heterogeneous group; with 1998 criteria, nearly one-half were high grade and the other half low grade. The grade of papillary urothelial carcinomas with both the 1973 and 1998 grading methods was associated with stage (P=0.001). Our study reveals that papillomas and papillary urothelial neoplasms of low malignant potential are uncommon tumors in the kidney. Renal pelvic papillary urothelial neoplasms are most often carcinomas and are more commonly high grade than low grade. Although both the 1973 and 1998 systems showed a significant association with tumor stage, grade 2 papillary carcinomas are a heterogeneous group by 1973 criteria. The 1998 system provides useful information in that it more clearly defines a papillary tumor's grade and selects for a group of tumors, namely low-grade papillary urothelial carcinomas, for which a low likelihood of invasion can be predicted.     

Prognostic markers in low-grade papillary urothelial neoplasms of the urinary bladder: an update

Papillary urothelial neoplasms of the urinary bladder comprise a heterogeneous spectrum of ‘continuous’ lesions in which the assessment of an accurate histological grade and tumour stage is mandatory for the clinical management of patients. The 1998 World Health Organization/International Society of Urologic Pathologists (WHO/ISUP) consensus classification and the 1999 WHO classification proposed new malignancy grading schemes, mainly based on morphometric studies for the replacement of the 1973 WHO grading system. In accordance with these novel grading systems, two major categories of papillary urothelial neoplasms were distinguished: low-grade and high-grade papillary urothelial neoplasms. Concerning the specific subgroup of low-grade tumours, two other entities were defined: papillary urothelial neoplasms of low malignant potential (PUNLMP) and low-grade papillary urothelial carcinomas (LGPUC). In long-term follow-up programmes, PUNLMP have demonstrated low recurrence rates and minimal risk for tumour progression in comparison with LGPUC. However, grade assessment is a subjective decision and, on occasion, the use of reproducible criteria by urological pathologists is difficult due to tumour heterogeneity and to the existence of a variable number of cases situated between consecutive groups. As a result, to determine a better correlation with clinicopathological patient outcome, other predictive markers are being investigated. Among these, the prognostic significance of classical clinicopathological, morphometric, cytometric, immunohistochemical and molecular markers have been widely reported. This review summarizes the prognostic importance of all these markers in the prediction of tumour recurrences and progression in low-grade papillary urothelial bladder neoplasms.     

Benign and low-grade papillary lesions of the urinary bladder: a review of the papilloma-papillary carcinoma controversy, and a report of five typical papillomas

The controversial topic concerning the most appropriate nomenclature for low-grade papillary lesions of the urinary bladder is reviewed on the basis of the literature and the authors' experiences. This undertaking was prompted by a recent report in which use of the designation "papilloma" was advocated for lesions that generally had been diagnosed as grade 1 papillary urothelial carcinoma. The literature indicates that 10% to 20% of patients with a noninvasive low-grade papillary tumor of the bladder will later have invasive bladder cancer. This significant outcome in a minority of such patients warrants very careful follow-up for the group as a whole, irrespective of the terminology used. The authors contrast the features of papillary urothelial carcinoma with a series of five cases, which they interpret as true papillomas. They believe that these low-grade papillary lesions can be distinguished from true papillomas and do not favor a change in terminology. Some of the problems in the evaluation of inverted papilloma and inverting urothelial carcinoma are briefly reviewed as are other selected papillary lesions of the urinary bladder.     

Atypia in inverted urothelial papillomas: pathology and prognostic significance

Inverted papillomas of the bladder are considered benign urothelial neoplasms, based on their histology and clinical course. There are scant data on inverted papillomas with atypical features. Whether to designate them as inverted papillomas with atypia or low-grade transitional cell carcinomas with inverted features is controversial. In the present study, 11 cases of inverted papillomas with atypia and 10 controls of classic inverted papillomas without atypia were collected from 2 institutions. The inverted papillomas with atypia had the typical architectural features of inverted papillomas consisting of thin anastomosing trabeculae of urothelium growing downward into the stroma without an exophytic papillary component. The atypical areas in the current series were focal, with other areas exhibiting the benign cytology of classic inverted papillomas. Cases with atypia were subdivided into the following groups: (1) 5 cases notable for areas containing prominent nucleoli, (2) 2 cases with foci with atypical squamous features, (3) 2 cases with areas of dysplasia, approaching the level of carcinoma in situ, (4) 1 case with degenerative-appearing multinucleated giant cells, and (5) 1 case notable for nests of atypical squamous cells associated with large, atypical squamoid cells with a pagetoid appearance in addition to degenerative-appearing multinucleated giant cells. Ki67 was slightly increased in 1 case, with focal dysplasia approaching carcinoma in situ and in 1 case with prominent nucleoli (increased Ki67 in both the atypical and non-atypical areas) and in the case with atypical squamous, pagetoid, and giant cells (no increased Ki67 in the atypical components). Two of the atypical inverted papilloma cases with prominent nucleoli demonstrated an increase in p53 staining throughout the lesions. Cytokeratin (CK) 20 staining was negative in all cases of inverted papillomas. No significant increase in Ki67 staining was found in any of the 10 control cases; increased p53 staining was seen in 1 control case. CK20 staining was negative in the 10 control cases. In the 11 cases with atypia, clinical follow-up revealed no history of prior or subsequent bladder neoplasms. In the cases reviewed, most inverted papillomas with atypia did not demonstrate significantly increased cellular proliferation in comparison with inverted papillomas without atypical features. To date, there has been no association with urothelial carcinoma in the individuals diagnosed with atypical inverted papillomas. These findings suggest that these lesions are currently best classified as inverted papillomas with atypia, not as low-grade transitional carcinomas, and that they merit continued evaluation as a distinct group.     

Genomic landscape of inverted urothelial papilloma and urothelial papilloma of the bladder

Inverted urothelial papilloma (IUP) and urothelial papilloma (UP) are rare urothelial neoplasms that typically follow a benign clinical course. Oncogenic mutations in FGFR3, HRAS, and the TERT promoter have been reported in these entities but no comprehensive molecular analysis has been performed. We sought to characterize the genomic landscape of IUP and UP using whole-exome and targeted next-generation sequencing. In IUP, 10 of 11 tumors harbored oncogenic hotspot mutations in HRAS and the remaining tumor had an oncogenic KRAS mutation. None of the IUP tumors harbored TERT promoter or FGFR3 mutations. In UP, 8 of 11 tumors had oncogenic KRAS mutations and two had oncogenic HRAS mutations. One UP tumor had oncogenic mutations in FGFR3, PIK3CA, and the TERT promoter, and arose in a patient with recurrent non-invasive papillary urothelial carcinomas. In contrast to urothelial carcinoma, the APOBEC mutational signature was not present in any IUP and UP tumors, and oncogenic alterations in chromatin remodeling genes were uncommon in both IUP and UP. The current study suggests that IUP and UP are driven primarily by RAS pathway activation and lack the more common genomic features of urothelial cancers. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

In ovarian neoplasms, BRAF, but not KRAS, mutations are restricted to low-grade serous tumours

Genes of the RAF family, which mediate cellular responses to growth signals, encode kinases that are regulated by RAS and participate in the RAS/RAF/MEK/ERK/MAP-kinase pathway. Activating mutations in BRAF have recently been identified in melanomas, colorectal cancers, and thyroid and ovarian tumours. In the present study, an extensive characterization of BRAF and KRAS mutations has been performed in 264 epithelial and non-epithelial ovarian neoplasms. The epithelial tumours ranged from adenomas and borderline neoplasms to invasive carcinomas including serous, mucinous, clear cell, and endometrioid lesions. It is shown that BRAF mutations in ovarian tumours occur exclusively in low-grade serous neoplasms (33 of 91, 36%); these included serous borderline tumours (typical and micropapillary variants), an invasive micropapillary carcinoma and a psammocarcinoma. KRAS mutations were identified in 26 of 91 (29.5%) low-grade serous tumours, 7 of 49 (12%) high-grade serous carcinomas, 2 of 6 mucinous adenomas, 22 of 28 mucinous borderline tumours, and 10 of 18 mucinous carcinomas. Of note, two serous borderline tumours were found to harbour both BRAF and KRAS mutations. The finding that at least 60% of serous borderline tumours harbour mutations in two members of the ERK-MAP-kinase pathway (BRAF 36%, KRAS 30%) compared with 12% of high-grade serous carcinomas (BRAF 0%, KRAS 12%) indicates that the majority of serous borderline tumours do not progress to serous carcinomas. Furthermore, no BRAF mutations were detected in the other 173 ovarian tumours in this study.     

Inverted urothelial papilloma of the urinary bladder with focal papillary pattern: a previously undescribed feature

We report 2 examples of inverted urothelial papillomas with a focal papillary pattern. Both patients, a 43-year-old man and a 13-year-old adolescent boy, presented with hematuria. In addition to the characteristic trabecular endophytic growth pattern and bland cytologic features, the tumors showed focal papillary architecture in the endophytic component. Because of this feature, both tumors were misinterpreted as papillary urothelial carcinoma with inverted pattern. However, the papillary fronds were similar to those of exophytic urothelial papilloma. They were lined by 3 to 8 layers of normal-appearing urothelial cells often covered by a continuous or discontinuous layer of superficial (umbrella) cells. Although follow-up is limited, the 2 patients have remained asymptomatic. The recognition of papillary structures in urothelial inverted papilloma broadens the morphological spectrum of this unusual benign urothelial neoplasm and complicates the microscopic interpretation of urothelial lesions with inverted growth patterns. Surgical pathologists should be aware of this unusual feature of inverted urothelial papilloma of the urinary bladder to avoid misinterpretation with urothelial carcinoma with an inverted pattern.     

Mutations in FGFR3 and PIK3CA, singly or combined with RAS and AKT1, are associated with AKT but not with MAPK pathway activation in urothelial bladder cancer

Different members of the phosphoinositide 3 kinase - serine threonine protein kinase (PI3K-AKT) pathway are altered in bladder cancer. Fibroblast growth factor receptor 3 (FGFR3) mutations characterize the low-grade tumors, and RAS genes are mutated in approximately 13% of all bladder tumors. Interestingly, a percentage of bladder tumors have alterations in more than 1 PI3K-AKT or rat sarcoma viral oncogene homolog-RAF mitogen activated protein kinase (RAS-MAPK) pathway gene or their upstream regulators, but some combinations are mutually exclusive. We analyzed mutations in FGFR3, phosphoinositide 3 kinase catalytic alpha polypeptide (PIK3CA), v-akt murine thymoma viral oncogene homolog 1 (AKT1), v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), v-Ha-ras Harvey rat sarcoma viral oncogene homolog (HRAS), and v-raf murine sarcoma viral oncogene homolog B1 (BRAF) in 88 urothelial cell carcinomas and the immunohistochemical expression of phospho-v-akt murine thymoma viral oncogene homolog (AKT) and mitogen-activated protein kinase 1 and 2 (pERK1/2) in 80 and 77 urothelial cell carcinomas, respectively. Approximately 43% and 20.5% of tumors presented 1 and 2 mutated genes, respectively. FGFR3 mutations were more frequent alone, whereas PIK3CA mutations were associated with another mutated gene (FGFR3 and KRAS). Overall, mutated FGFR3 (FGFR3(mut)) and mutated FGFR3 (FGFR3(mut))-mutated PIK3CA (PIK3CA(mut)) genotypes were associated with low-grade bladder tumors and mutated PIK3CA (PIK3CA(mut))-mutated KRAS (KRAS(mut)) and mutated AKT1 (AKT1(mut)) were only present in high-grade tumors. There are no mutated FGFR3 (FGFR3(mut))-mutated RAS (RAS(mut)) nor mutated PIK3CA (PIK3CA(mut))-mutated AKT1 (AKT1(mut)) combinations. Fifty percent and 56% of tumors showed high levels of pAKT and pERK1/2, respectively. High levels of pAKT were associated with total mutations, FGFR3(mut), and PIK3CA(mut) tumors but not with tumor grade or stage. Wild-type tumors presented significantly higher pERK1/2 expression. Mutations in FGFR3 and FGFR3-PIK3CA but not single PIK3CA mutations characterize low-grade bladder tumors. Single FGFR3 or PIK3CA mutations and the different mutation combinations FGFR3-PIK3CA/AKT1 and PIK3CA-RAS can activate the AKT but not the MAPK pathway. Other genes different from FGFR3 may be related with the pERK activation in bladder tumors.     

Papillary urothelial neoplasm of low malignant potential of the urinary bladder: clinicopathologic and outcome analysis from a single academic center

Few long-term single-center studies have addressed the outcome of patients with papillary urothelial neoplasms of low malignant potential. Our study evaluates the behavior of these tumors occurring as primary urinary bladder lesions. For this purpose, 34 primary in-house cases diagnosed and treated between 1998 and 2008 were identified from our medical records. Upon review, 3 cases were upgraded to noninvasive low-grade urothelial carcinomas and excluded from further evaluation. During follow-up (range, 3-108 months; mean, 42 months), 13 patients developed recurrences; and 9 patients progressed to a noninvasive higher grade lesion (8 to low-grade and 1 to high-grade urothelial carcinomas). None of our patients developed stage progression (>pTa) or died of bladder cancer. Size of the primary tumor was associated with the risk of recurrence (P = .043), whereas the number of episodes of recurrence was associated with the likelihood of grade progression (P = .034). In conclusion, recurrences were observed in 42% of all our patients, with a grade progression rate of 29%. None of our patients developed invasive carcinoma or died as a consequence of their disease. Considering the low but definitive risk of recurrence and grade progression, appropriate clinical follow-up of patients with primary papillary urothelial neoplasm of low malignant potential is warranted.     

Neuerungen in der histologischen WHO-Klassifikation urothelialer Harnblasentumoren und abnormer flacher Urothelläsionen

Recently the World Health Organization published a new classification of urinary bladder tumors which is intended to take into account better the biology of the various lesions and to better distinguish between clearly benign and malignant lesions. We examine the possible diagnostic and clinical impact of the new classification, including recent immunohistochemical findings. Papillary urothelial lesions include papillomas, papillary neoplasms of low malignant potential, and papillary carcinomas. Flat urothelial lesions include hyperplasia, reactive atypia/atypia of unknown significance, dysplasia, and carcinoma in situ. Invasive patterns of papillary carcinomas are discussed, with special emphasis on lamina muscularis mucosae substaging. The most important feature of the new classification is its differentiation of two types of low-grade, noninvasive papillary urothelial lesions: papillary neoplasm of low malignant potential vs. papillary carcinoma. Long-term follow-up studies are needed to determine the clinical significance of this differentiation.     

A multistep model for ovarian tumorigenesis: the value of mutation analysis in the KRAS and BRAF genes

Epithelial ovarian tumours represent a complex group of histological subtypes and there has long been controversy over the question of a precursor lesion for these neoplasms. The application of mutation analysis of the KRAS and BRAF genes (members of the RAS-RAF-MEK-ERK-MAP kinase pathway) is consistent with the model for progression of mucinous carcinomas and a subset of serous carcinomas (the so-called low-grade serous carcinomas) through benign and borderline lesions. The relatively high incidence of BRAF and KRAS mutations in serous borderline tumours and low-grade serous carcinomas, and their extremely low incidence/absence in high-grade serous carcinomas, provide strong evidence that high-grade carcinomas do not arise through this intermediate step.     

CDKN2A homozygous deletion is associated with muscle invasion in FGFR3-mutated urothelial bladder carcinoma

The gene cyclin-dependent kinase inhibitor 2A (CDKN2A) is frequently inactivated by deletion in bladder carcinoma. However, its role in bladder tumourigenesis remains unclear. We investigated the role of CDKN2A deletion in urothelial carcinogenesis, as a function of FGFR3 mutation status, a marker for one of the two pathways of bladder tumour progression, the Ta pathway. We studied 288 bladder carcinomas: 177 non-muscle-invasive (123 Ta, 54 T1) and 111 muscle-invasive (T2-4) tumours. CDKN2A copy number was determined by multiplex ligation-dependent probe amplification, and FGFR3 mutations by SNaPshot analysis. FGFR3 mutation was detected in 124 tumours (43.1%) and CDKN2A homozygous deletion in 56 tumours (19.4%). CDKN2A homozygous deletion was significantly more frequent in FGFR3-mutated tumours than in wild-type FGFR3 tumours (p = 0.0015). This event was associated with muscle-invasive tumours within the FGFR3-mutated subgroup (p < 0.0001) but not in wild-type FGFR3 tumours. Similar findings were obtained for an independent series of 101 bladder carcinomas. The impact of CDKN2A deletions on recurrence-free and progression-free survival was then analysed in 89 patients with non-muscle-invasive FGFR3-mutated tumours. Kaplan-Meier survival analysis showed that CDKN2A losses (hemizygous and homozygous) were associated with progression (p = 0.0002), but not with recurrence, in these tumours. Multivariate Cox regression analysis identified CDKN2A loss as a predictor of progression independent of stage and grade. These findings highlight the crucial role of CDKN2A loss in the progression of non-muscle-invasive FGFR3-mutated bladder carcinomas and provide a potentially useful clinical marker for adapting the treatment of such tumours, which account for about 50% of cases at initial clinical presentation.     

Inverted urothelial papillomas with foamy or vacuolated cytoplasm

Inverted papillomas of the bladder are uncommon benign neoplasms characterized by endophytic growth of urothelial cells as anastomosing cords, displaying minimal cytologic atypia. Reports of inverted papilloma associated with urothelial carcinoma or urothelial carcinoma arising within inverted papilloma highlight the difficulties in evaluating urothelial lesions with inverted growth patterns. Within the spectrum of findings in inverted papilloma, vacuolization and foamy (xanthomatous-appearing) cytoplasmic changes have not been previously reported. In the current study, we present 5 novel cases of inverted papilloma involving 2 men and 3 women ranging in age from 48 to 88 years, who presented with microhematuria (n = 3) or irritative symptoms (n = 2). Cystoscopically, the lesions were polypoid (n = 3), pedunculated (n = 1), or solid (n = 1), measured between 0.7 and 2.5 cm, and were all located at the trigone or bladder neck. Morphologically, all cases had some component of usual inverted papilloma along with areas displaying foamy or vacuolated cytoplasm encompassing 30% to 90% of the lesion. These "clear cells" were seen both in distinct regions within the biopsy and, more frequently, intermingled with usual inverted papilloma cells. In 3 of 5 cases, these findings were sufficiently unusual to cause confusion with urothelial carcinoma. The diagnostic dilemma encountered in these cases of inverted papilloma with foamy or vacuolated cytoplasm warrants their distinction from other benign and malignant urothelial lesions with inverted growth and/or clear cell features.     

Histologic grading of noninvasive papillary urothelial tumors: validation of the 1998 WHO/ISUP system by immunophenotyping and follow-up

Cytokeratin (CK) 20, Ki-67, and p53 were applied to 84 noninvasive papillary urothelial tumors graded by the 1973 World Health Organization (WHO) and 1998 WHO/International Society of Urological Pathology (ISUP) systems. In the WHO/ISUP classification, all benign lesions showed normal CK20 staining and all carcinomas showed abnormal staining. The Ki-67 index was significantly different between benign and malignant lesions (P < .05) and between low- and high-grade carcinomas (P < .001). p53 was negative in all benign lesions, with a significant difference between low- and high-grade carcinomas (P < .001). Tumor recurrence was significantly different between low- and high-grade carcinomas (no recurrences among the papillary urothelial neoplasms of low malignant potential). By the 1973 WHO classification, normal CK20 staining was present both in benign lesions and in carcinomas. Ki-67 staining did not distinguish between grade 2 and grade 3 carcinomas (P > .05), and there was no difference in p53 staining in grades 1 and 2 carcinomas (P > .05). Recurrences were not different between grades 1, 2, and 3 carcinomas. All biologic markers studied and tumor recurrences were significantly different among papillary lesions classified by the WHO/ISUP system but not by the 1973 WHO system, validating the predictive value of the WHO/ISUP system and providing objective markers for the grading of papillary urothelial tumors.     

DNA study of bladder papillary tumours chemically induced by N-butyl-N-(4-hydroxybutyl) nitrosamine in Fisher rats

To examine DNA abnormalities in bladder papillary tumours induced by N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in female rats, using image cytometric DNA analysis and cytogenetics. Thirty female rats were exposed to BBN in their drinking water for 20 weeks. One group of 10 animals served as controls. The animals exposed to BBN were killed at a rate of two per week, with the bladder being collected under aseptic conditions and those tumours with exophytic growth removed. The nuclear DNA content of the tumours was evaluated using image cytometric analysis. In two rats part of the tumour pieces was stipulated for culturing. Cytogenetic analysis was performed on at least 30 cells from each cell population and on both tumours. Papillary carcinomas were classified as low grade and high grade. DNA ploidy studies were carried out on 28 low-grade and 21 high-grade papillary carcinomas. Histograms obtained by image analysis showed that a normal urothelium was diploid; 28.6% and 100% of low-and high-grade papillary carcinomas were aneuploid respectively. Both tumours used for cell culture showed multiple numerical and structural chromosome alterations and several marker chromosomes. Image cytometric DNA analysis proved to be a good and reliable method for examining DNA alterations in papillary bladder carcinomas. The present findings establish that the DNA content is statistically different between low-grade and high-grade papillary carcinomas and that deviation from the diploid number is markedly higher in the high-grade ones. In addition, the occurrence of marker chromosomes seems to be related to the aggressiveness of the tumour.