Pathology of tumours of the kidney and urinary tract

The urinary tract encompasses the kidney and the urinary collecting system, ureter, bladder and urethra. Benign lesions of the kidney include angiomyolipoma and renal oncocytoma. The main subtypes of renal cell carcinoma include clear cell, papillary and chromophobe variants. Prognostic factors reported by pathologists are reviewed, including the current grading and staging systems. Urothelial tumours include urothelial carcinoma in situ, papillary urothelial carcinoma, and invasive urothelial carcinoma. Aspects of their grading and staging are covered, and several less common variants and benign urothelial lesions are mentioned. General aspects of core biopsy and resection specimens for renal disease are examined, including indications for frozen section examination.     

Pathology of tumours of the kidney and urinary tract

The urinary tract encompasses the kidney and the urinary collecting system, ureter, bladder and urethra. Benign lesions of the kidney include angiomyolipoma and renal oncocytoma. The main subtypes of renal cell carcinoma include clear cell, papillary and chromophobe variants. Prognostic factors reported by pathologists are reviewed, including the current grading and staging systems. Urothelial tumours include urothelial carcinoma in situ, papillary urothelial carcinoma and invasive urothelial carcinoma. Aspects of their grading and staging are covered, and several less common variants and benign urothelial lesions are mentioned. General aspects of core biopsy and resection specimens for renal disease are examined, including indications for frozen section examination.     

Renal cell carcinoma invading the urinary collecting system: implications for staging

PURPOSE: Current TNM staging of renal cell carcinoma is based on the tumor propensity for local extension (T), nodal involvement (N) and metastatic spread (M). Locally advanced renal cell carcinoma may involve the perirenal fat, adrenal glands, renal vein, vena cava and/or urinary collecting system. The existing TNM classification does not reflect the ability of renal cell carcinoma to invade the urothelium. We evaluated the incidence and characteristics as well as overall and cancer specific survival of renal cell carcinoma invading the urinary collecting system. METHODS AND MATERIALS: We reviewed pathological findings in 504 kidneys from 475 patients with renal cell carcinoma who presented to our institution in a 3-year period. Urothelial involvement required evidence of gross or histological invasion of the renal calices, infundibulum, pelvis or ureter. Demographic and survival data were obtained from medical records and an institutional cancer registry for tumors invading the urothelium. Stage specific survival data were then compared with tumors not involving the urinary collecting system. RESULTS: Definitive urothelial involvement by the primary tumor was interpretable in 426 of 504 kidneys. Invasion of the collecting system was identified in 61 of 426 cases (14%). Mean diameter of the invading lesions was 10.2 cm. (range 3 to 26). The majority of cases showed clear cell and sarcomatoid histology. Invasion by a papillary lesion was rare. Involvement of the collecting system was most common at the renal poles. Of 61 lesions invading the collecting system 48 (79%) were stage pT3 or greater, while only 13 (21%) were pathologically localized stage pT2 or less. Vascular invasion was identified in 38 renal cell carcinoma cases (62%) with urothelial involvement. A total of 16 cases (26%) were associated with vena caval thrombus. Invading tumors were high Fuhrman grade III or IV in 43 cases (70%). Overall disease specific survival was poor with a median of 19 months. In patients with localized stage pT1 or pT2N0M0 disease and urothelial invasion median disease specific survival was 46 months. CONCLUSIONS: Renal cell carcinoma lesions involving the renal collecting system are characteristically large, high grade and high stage. Clear cell carcinoma most commonly invades, while invasion by papillary tumors is rare. Overall the prognosis for high stage lesions with urothelial involvement is poor and does not appear significantly different from the reported disease specific survival of patients with high stage lesions without urothelial invasion. Localized tumors 4 cm. or less, which are amenable to elective nephron sparing surgery, rarely invade the urothelium. However, when a low stage pT2 or less renal lesion involves the urinary space, survival appears worse than equivalently staged renal cell carcinoma without invasion. Including urothelial invasion into current TNM staging systems for renal cell carcinoma is unlikely to provide significant additional prognostic or therapeutic information.     

Neuerungen in der histologischen WHO-Klassifikation urothelial 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.     

Urothelial carcinoma (clear cell variant) diagnosed with useful immunohistochemistry stain

The case is reported of urothelial carcinoma (clear cell variant) that was diagnosed with useful immunohistochemistry stain. A 70-year-old man, who had undergone left radical nephrectomy for renal cell carcinoma in August 2003 and partial lobectomy for pulmonary metastasis in May 2005, complained of hematuria in June 2005. On evaluation, a papillary pedunculated tumor was detected in the left wall of the urinary bladder. A transurethral resection of the bladder tumor (TUR-Bt) was performed in July 2005. The pathological diagnosis was difficult due to diffuse clear cell appearance. Immunohistochemistry stain showed urothelial carcinoma, not metastasis of the renal cell carcinoma. Finally it was diagnosed as urothelial carcinoma clear cell variant. Urothelial carcinoma has many variants that show a variety of appearances and characteristics. These should be well known before medical therapy is initiated.     

Hemorrhagic infarction of the kidney. An uncommon presentation of infiltrating urothelial carcinoma of the renal pelvis

A case of infiltrating urothelial carcinoma of the renal pelvis presenting the pathologic picture of hemorrhagic infarction of the kidney is reported. The physiopathologic mechanisms of this presentation are discussed. It is suggested that urothelial carcinoma be included in the differential diagnosis during the work-up of renal lesions suspected of being papillary necrosis or hemorrhagic infarction.     

Genitourinary Malignancies in Transplant or Dialysis Patients: The Frequency of Two Newly Described 2016 World Health Organization Histopathologic Types

Background

The aim of this study was to revise the histopathologic types of neoplasias in the genitourinary tract and determine the frequency of 2 new entities included in the 2016 book of World Health Organization classification of renal tumors. It is not established so far whether these 2 recently described tumors are the most frequent in association with end-stage kidney disease.

Multifocality in renal cell carcinoma: A bilateral event?

OBJECTIVES: The major disadvantage of nephron-sparing surgery for renal cell carcinoma is the risk of local recurrence. This is most likely a manifestation of undetected small additional tumors in the renal remnant. To define more clearly the incidence and nature of unilateral and bilateral multifocal tumors, an autopsy study was undertaken. MATERIALS AND METHODS: In a series of 14,793 autopsies from 1985 to 1995, 260 renal cell carcinomas were found. In all cases of renal cell carcinoma a search for small renal lesions was performed in the apparently normal-appearing portion of the kidneys. Every kidney was serially and systematically cut (5 mm) to probe for intraparenchymal lesions. RESULTS: Of the 260 renal cell carcinomas 36 cases (13.85%) had multifocal malignant and/or benign nodules. The number of the additional nodules ranged from 2 to 18. 12% of the malignant multifocal carcinomas were limited to the ipsilateral kidney and 88% were bilateral. The average size of the multifocal renal lesions was 8.7 x 9.0 x 9.5 (range 3-23) mm. Renal cell carcinomas with low stage and good grading have a higher incidence of multifocal nodules. No significant difference was found with regard to metastasized and nonmetastasized renal cell carcinomas. In 38.1% of all chromophilic renal cell carcinomas additional nodules were found. CONCLUSIONS: Multifocality in renal cell carcinomas cannot be predicted reliably, although the papillary histological pattern, good grading and low staging seems to be associated with a higher incidence of multifocality. Nearly 90% of the multifocal nodules were bilateral.     

Role of lymphadenectomy in the management of urothelial carcinoma of the bladder and the upper urinary tract

The role of lymphadenectomy has been controversial in urological malignancies. Urothelial carcinoma of the bladder and upper urinary tract has a high potential to spread through the lymphatic network compared with other malignancies, including renal cell carcinoma or prostate cancer. In urothelial carcinoma of the bladder, lymphadenectomy of pelvic nodes had been considered as the standard procedure when radical cystectomy was carried out. Recently, many investigators have examined the influence of its extent, and the majority of the studies have supported the beneficial role of extended lymphadenectomy in accurate staging or in improving patient survival. Although randomized controlled trials are required to establish a greater level of evidence, more urological surgeons have already noticed the necessity for extended lymphadenectomy in bladder cancer. In contrast to bladder cancer, there have been far fewer studies on urothelial carcinoma of the upper urinary tract. This might be because of the smaller number of the patients with urothelial carcinoma of the upper urinary tract and the lack of understanding of regional nodes. However, studies of lymph node mapping and the retrospective analyses with respect to the benefit of lymphadenectomy have been carried out in urothelial carcinoma of the upper urinary tract by some investigators, although the results are still controversial. However, the results from multi‐institutional studies by high volume centers have supported the beneficial role of lymphadenectomy in urothelial carcinoma of the upper urinary tract, as it has been proposed in bladder cancer. Thus, lymphadenectomy for urothelial carcinoma of the bladder and the upper urinary tract might have a potential role in staging and improving the oncological outcomes.     

Overexpression of p27kip1 in urinary bladder urothelial carcinoma

OBJECTIVES: Cyclins and cyclin-dependent kinase (CDK) complexes have important regulatory roles during cell cycle progression and can be used as prognostic markers in various kinds of malignant tumors. This study investigated the expression of proliferative cell nuclear antigen (PCNA), p53, Rb, p27(kip1), and cyclin D1 by immunostains in bladder tumors, especially urothelial papilloma, papillary urothelial neoplasm of low malignant potential, and low and high grade urothelial carcinoma, to see if their expression is associated with classification or grading of the urinary bladder urothelial carcinoma. METHOD: Nuclear expression of PCNA, p53, Rb, p27(kip1), and cyclin D1 was determined immunohistochemically in a series of 89 urinary bladder tumor specimens, including 13 papilloma, 15 urothelial neoplasm of low malignant potential, 17 low grade urothelial carcinoma, and 44 high grade urothelial carcinoma. The results of immunoreactivity were analyzed with respect to the associations with tumor grade. RESULTS: Eighty-two percent (38/45) of the p27(kip1) positive tumors were urothelial carcinoma, and the percentage of the p27(kip1) positivity was higher with increasing grade of the urothelial carcinoma (P = 0.011). A tendency of higher percentage of positive p53 immunoreactivity was noted in the urothelial carcinoma (P = 0.053). There was no significant difference in cyclinD1, Rb and PCNA expression between benign, low malignant potential and urothelial carcinoma. CONCLUSION: We first noted an overexpression of p27(kip1) in urinary bladder urothelial carcinoma. The result indicates that some urothelial carcinomas may tolerate this inhibitor of cell cycle progression.     

Computerized tomography for detection and staging of localized and pathologically defined upper tract urothelial tumors

Between 1980 and 1989, 94 patients were evaluated for upper tract urothelial tumors. Preoperative computerized tomography (CT) scans and pathology reports were available in 30 patients who also had nephroureterectomy for treatment of transitional cell carcinoma. Retrospective evaluation of these CT scans was done without knowledge of the final pathological status to determine accuracy of tumor detection and staging. Pathological findings were also reviewed and the pathological staging was compared to that of CT. At pathological evaluation the 30 renal units contained 34 grossly visible, distinct papillary tumors: 7 were ureteral and 27 were in the renal pelvis. Of the renal units 8 also contained carcinoma in situ that was not visible on any study. Conventional excretory urograms and/or retrograde or antegrade pyelograms detected 28 (82%) and CT 17 (50%) of the 34 papillary tumors. Excluding suboptimal scans due to early generation machines, inadequate intravenous contrast medium or too widely spaced slices caused CT sensitivity to increase to 15 of 22 (68%). It was not possible to distinguish stages Ta to T2 lesions on any radiological study. CT sensitivity for parenchymal invasion was 75% with a specificity of 43%. CT sensitivity for fat invasion was 67% with a specificity of 44%. We conclude that CT is limited in usefulness for detection and staging of low stage upper tract urothelial tumors. While CT is the best current imaging modality over-all for staging of upper tract urothelial tumors, results obtained in low stage tumors must be viewed with caution particularly when precise preoperative clinical staging is essential, such as before nephron-sparing procedures.     

Significance of denuded urothelium in papillary urothelial lesions

Flat urothelial carcinoma in situ (CIS) is often characterized by prominent dyscohesion with some cases having only a few clinging CIS cells remaining on biopsy. The finding of extensive denudation on urothelial biopsies is associated with a risk of CIS on either prior or subsequent biopsies. The significance of denudation in papillary urothelial lesions has not been formally studied. We identified from our surgical pathology files 31 specimens (from 28 patients) of papillary urothelial lesions with extensive denudation. In cases in which denudation was associated with low-grade urothelial neoplasms, follow-up of subsequent cytologic and histologic specimens was obtained. Of the 28 patients, 25 (89%) were men and 3 (11%) were women with an age range of 40 to 88 years old (mean age 62). Of 31 biopsies, 15 were from anatomically confined areas (ie, renal pelvis, ureter, and urethra). In 22/28 (79%) patients, prominent denudation was associated with high-grade papillary carcinomas, 4/28 (14%) low-grade papillary carcinomas, and 2/28 (7%) papillary urothelial neoplasms of low-grade malignant potential. The average extent of urothelial denudation was 82% with 61% of cases having > or =90% denudation. Prominent cautery artifact was present in 17/31 (55%) cases. In 13/28 patients with high-grade lesions, there was a concurrent biopsy of a second urothelial lesion that was either high-grade papillary urothelial carcinoma or invasive urothelial carcinoma. Five of the 6 patients in which the prominent denudation was associated with a low-grade papillary urothelial lesion have not progressed to a high-grade lesion. One patient with a denuded papillary urothelial neoplasm of low malignant neoplasm was subsequently diagnosed with a noninvasive low-grade papillary urothelial carcinoma in the bladder and a high-grade infiltrating urothelial carcinoma of the ureter. We conclude that (1) the majority of papillary urothelial lesions associated with prominent urothelial denudation are high grade; (2) a significant percentage of papillary urothelial lesions with denudation occur with either prominent cautery artifact or in anatomically confined areas, suggesting both iatrogenic and mechanical contributing factors, respectively; (3) a minority of cases with prominent urothelial denudation occur in association with low-grade papillary urothelial lesions and are not associated with progression to higher grade lesions on follow-up studies; and (4) prominent urothelial denudation in papillary lesions should prompt careful examination of these specimens for rare clinging high-grade carcinoma cells, although in a minority of cases the underlying lesion will be low grade.     

Expression of alpha-methylacyl-CoA racemase in papillary renal cell carcinoma

Alpha-methylacyl-CoA racemase (AMACR) was first discovered by using cDNA microarray technology as a molecular marker for prostate cancer. Our recent microarray analysis of renal cell carcinomas showed a significant increase of AMACR mRNA levels in papillary renal cell carcinomas, but not in other subtypes. To investigate the value of this marker in pathologic diagnosis, we analyzed AMACR mRNA levels in cDNA microarrays from 70 kidney tumors. Furthermore, we evaluated the AMACR expression in 165 kidney tumors on tissue microarrays and 51 papillary carcinomas of other organs by immunohistochemistry. AMACR mRNA was significantly overexpressed in 7 of 8 papillary renal cell carcinomas with an average of 5.2-fold increase, and only in 2 of 62 nonpapillary kidney tumors. Immunohistochemistry demonstrated strong AMACR positivity in all cases of papillary renal cell carcinomas (41 of 41, 100%), including 6 metastatic papillary renal cell carcinomas, but only focal or weak reactivity in the minority (18 of 124, 15%) of other renal tumors including 13 of 52 clear cell renal cell carcinomas, 3 of 20 oncocytomas, and 2 of 17 urothelial carcinomas. All chromophobe (0 of 18) and sarcomatoid components of renal cell carcinomas (0 of 15) were negative for AMACR. Weak or focal AMACR immunoreactivity was detected in only 4 of 51 (8%) papillary carcinomas arising in other organs (2 of 14 thyroid, 2 of 13 lung, 0 of 6 breast, 0 of 6 endometrium, 0 of 6 ovary, and 0 of 6 pancreas). Using a combination of cDNA microarrays, tissue microarrays, and immunohistochemistry, we identified AMACR as a marker for papillary renal cell carcinoma, which could be valuable in subclassification of renal cell carcinomas and in the differential diagnosis of a metastatic papillary carcinoma.     

Diagnostic implications of transcription factor Pax 2 protein and transmembrane enzyme complex carbonic anhydrase IX immunoreactivity in adult renal epithelial neoplasms

Pax 2, expressed by metanephric mesenchyme is vital for renal tubule formation and development. Carbonic anhydrase IX (CA IX) is implicated in cell proliferation, adhesion, and invasion. Data regarding expression in renal epithelial tumors other than clear cell renal cell carcinoma (RCC) are limited, conflicting, from tissue microarrays, and do not encompass the entire spectrum or novel uncommon variants. Conventional sections from 200 renal tumors comprising clear cell RCC (n=30), oncocytoma (n=17), papillary RCC (n=30), chromophobe RCC (n=50), urothelial carcinomas (n=30), collecting duct carcinomas (n=5), renal tumors with Xp11.2 translocation (n=15), tubulocystic carcinoma (n=19), and mucinous tubular spindle cell carcinoma (n=4) were immunostained for Pax 2 and CA IX. Clear cell RCC (28/30, 93%), oncocytoma (17/17, 100%), papillary RCC (16/30, 53%), and mucinous tubular spindle cell carcinoma (3/4, 75%) demonstrated nuclear immunoreactivity with Pax 2, whereas the other subtypes were nonreactive. Clear cell RCC (30/30, 100%), urothelial carcinoma (27/30, 90%), papillary RCC (17/30, 57%), and renal tumors with Xp11.2 translocation (6/15, 40%) exhibited membranous immunoreactivity with CA IX, whereas the other subtypes were nonreactive. This suggests potential diagnostic utility of Pax 2 in distinction of (i) oncocytoma (positive) from chromophobe RCC (negative), (ii) clear cell RCC and papillary RCC (positive) from renal tumors with Xp11.2 translocation (negative), and (iii) high-grade clear cell RCC (positive) from urothelial carcinoma (negative). CA IX expression has potential diagnostic implications including (i) clear cell RCC (positive) versus chromophobe RCC (negative) and (ii) urothelial carcinoma (positive) versus collecting duct carcinoma (negative). These antibodies may reliably discriminate between clinically significant subtypes of RCC with overlapping cytoarchitectural features.     

Ureteroscopic approach to upper-tract urothelial tumors

Transitional-cell carcinoma (TCC) of the upper urinary tract has traditionally been managed by nephroureterectomy, whereas nephron-sparing surgery has been reserved for those few patients with solitary kidneys or bilateral lesions. However, with the introduction of improved diagnostic and therapeutic technology, including smaller ureteroscopes and working instruments, and the concomitant ease of surveillance, ureteroscopic treatment of upper-tract urothelial tumors has become a reasonable alternative to open operative intervention in patients requiring conservative management. Furthermore, as preoperative grading and staging have improved, ureteroscopic treatment of upper-tract urothelial tumors is assuming an increasingly important role in the management of some patients who might have otherwise been treated with a nephroureterectomy. The technique of ureteroscopic resection is described in detail.