Clear cell adenocarcinoma of urinary bladder and urethra: another urinary tract lesion immunoreactive for P504S

Diagnostic Approach to and Differential Diagnosis of Clear Cell and Glandular Lesions of the Lower Urinary Tract

CONTEXT.—

A variety of glandular and clear cell lesions may be seen in the urinary bladder and/or urethra, ranging from benign to malignant primary and secondary tumors. Lesions with no malignant potential include reactive processes, such as nephrogenic metaplasia, and may show similar morphologic features as an infiltrative neoplasm, particularly in small biopsies. Similarly, ectopic tissues of Müllerian origin may be seen in the lower urinary tract, and their distinction from a true glandular neoplasm is essential to avoid overtreatment. A wide variety of primary and secondary malignant tumors exist with varying degrees of glandular and clear cell features. Therefore, surgical pathologists must be aware of the full scope of possible lesions to avoid misdiagnosis.

OBJECTIVE.—

To provide a practical framework for approaching the diagnosis of clear cell and glandular lesions of the urinary bladder/urethra and prostate, highlighting the strengths and limitations of various diagnostic features and ancillary tests.

DATA SOURCES.—

A review of the current literature was performed to obtain data regarding up-to-date diagnostic features and ancillary studies.

CONCLUSIONS.—

In summary, distinct morphologic and immunohistochemical features and clinical and radiologic correlation are essential to establish an accurate diagnosis when such cases with glandular and clear features are encountered in the lower urinary tract.

Ureteral Metastasis of Colonic Adenocarcinoma with Enteroblastic Differentiation: A Rare Case to be Distinguished from Clear Cell Adenocarcinoma of the Urinary Tract

Adenocarcinomas with enteroblastic differentiation are rare clear cell tumors that are positive for enteroblastic markers. Enteroblastic differentiation is particularly uncommon in colorectal adenocarcinomas. Herein, we report a case of clear cell adenocarcinoma with enteroblastic differentiation in the sigmoid colon of a 38-year-old Japanese woman that metastasized to the lower left ureter. After neoadjuvant chemotherapy, the patient underwent low anterior resection. The tumor consisted of tubular, cribriform, and focal micropapillary proliferation of clear cells immunopositive for spalt-like transcription factor 4 (SALL4), glypican 3, and alpha-fetoprotein. Six months after the colonic resection, a tumor was found in the left lower ureter, which was resected. The ureteral tumor revealed clear cell adenocarcinoma, which was identical to the colonic tumor proliferating in the ureteral mucosa. Metastatic ureteral tumors are rare. We performed a literature search and found only 50 reported cases of ureteral metastases from colorectal cancer. Of these, only 10 metastatic tumors were identified in the ureteral mucosa. No case of ureteral metastasis of clear cell colorectal adenocarcinoma or colorectal adenocarcinoma with enteroblastic differentiation has been reported. Hence, it can be challenging to distinguish them from clear cell adenocarcinoma of the urinary tract and/or clear cell urothelial carcinoma. This paper discussed the differential diagnosis of these tumors and reviewed the clinicopathological features of colorectal carcinomas metastasizing to the ureter.

Clear cell adenocarcinoma of the male urethra: a case report

Background

Primary urethral cancer in males is rare. Clear cell adenocarcinoma is more rare. We report a case in an African male suspected to have a urethral stricture.

Case presentation

A 66-year-old man presented in with preceding intermittent haematuria and acute urinary retention. Failed attempts at catheterisation necessitating a suprapubic catheter insertion raised the suspicion of a urethral stricture. Multiple irregular urethral filling defects were seen on a retrograde urethrogram. Urethroscopy revealed obstructing urethral masses. Histology reported clear cell adenocarcinoma.

Conclusion

Primary urethral cancer should be entertained as a differential diagnosis of a urethral stricture in a patient with haematuria, difficult urethral catheterisation and ambiguous urethrogram findings. Cystoscopy and biopsy are essential in the investigative work-up to make the distinction.

Primary clear cell adenocarcinoma of prostate: A diagnostic challenge

Clear cell adenocarcinoma (CCA) rarely occurs in men, not to mention in prostate. We reported a 44-year-old male patient who suffered from recurrent dysuria and frequency for 6 months. Transurethral resection of the prostate was performed to relieve bladder outlet obstruction. However, CCA of the prostate was confirmed through pathological examination. A thorough checkup was performed to distinguish it from metastatic clear cell carcinoma from other primary origins. Currently, no consensus for the treatment of CCA of the prostate has been reached. After discussing with the patient, he decided to receive immunotherapy with pembrolizumab. Herein, we reported this rare case of CCA in the prostate.

Clear Cell Adenocarcinoma in Men: A Series of 15 Cases

Clear cell adenocarcinoma (CCA) is a rare tumor in the genitourinary tract with female predominance and few reports in men. We identified 15 cases of CCA in men evaluated at our institution. Five arose in the bladder, 7 in the prostate or prostatic urethra, 2 in the membranous urethra (1 multifocal in the prostatic and membranous urethra), 1 periprostatic (likely from an embryologic remnant), and 1 between rectum and bladder (likely in a prostatic utricle cyst). No cases showed associated Müllerian structures. One case showed separate foci of nephrogenic adenoma at diagnosis, and 1 case showed urothelial carcinoma in situ on a later follow-up biopsy. Four tumors extended into other organs (prostate to seminal vesicle and periprostatic soft tissue, periprostatic soft tissue to prostate, prostatic urethra to bladder and rectum, and prostate to bladder neck). One tumor showed extraprostatic extension alone. Four tumors metastasized to lymph nodes, with 3 also metastasizing to other sites (bladder, lung and adrenal, and right flank). Eleven patients underwent resection, including 3 transurethral resections. Seven underwent other treatments, including radiation (5 [1 for recurrence]), chemotherapy (3), hormonal therapy (3), immunotherapy with nivolumab (1), and targeted therapy with gefitinib (1). The mean follow-up was 35 months (range: 1 to 138 mo). At the last follow-up, 7 patients showed no evident disease and 3 were alive with disease. Four died with the cause of death unknown, with 2 cases having confirmed disease at the time of death and the remaining 2 dying less than a year after diagnosis. The mean time to death was 16 months (range: 6 to 39 mo). No follow-up was available on 1 patient. All patients who died in this series had CCA of the prostate or prostatic urethra. Pathologists need to be attuned to CCA occurring in males, given that the literature emphasizes its occurrence in females. In addition to established sites such as bladder and urethra, our series demonstrates that tumor may present in unusual adjacent sites, such as in periprostatic embryologic remnants or prostatic utricle.

Clear cell carcinoma of the urinary bladder: a systematic review

PURPOSE

We conducted a systematic review of the literature on primary clear cell carcinoma (CCC) of the urinary bladder.

METHODS

A literature search using keywords and MeSH terms related to "clear cell carcinoma", "clear cell adenocarcinoma", "mesonephroma" and "urinary bladder" in EMBASE, MEDLINE and Cochrane Central Register of Controlled Trials was performed. A manual search was performed with web-based search engine Google Scholar. Reference lists of the included studies were screened for additional articles. Articles up till 16th July 2020 were retrieved. Observational human studies on primary CCC in urinary bladder with English full-text were included for further analysis.

RESULTS

904 articles were identified and 44 articles were included for further analysis. Data including clinical features, tumour characteristics, treatment and oncological outcomes were reviewed. There were 70 patients (44 females and 26 males) reported in literatures and included in this review. Gross haematuria was the most common presentation (79.7%), followed by irritative urinary symptoms (47.5%). Regarding the histology, tubulocystic pattern is the most common histologic pattern (49.1%), and 52.6% had muscle invasion. Most cases were CK7 (96.6%) and CK20 (88.9%) positive. CA125 (96%) was commonly positive, indicating its potential origin from mullerian duct. Most patients received surgery (95.5%) as primary treatment. However, the oncological outcomes were unsatisfactory with a 2-year survival rate of 60.0%.

CONCLUSION

Clear cell carcinoma is an uncommon subtype of bladder cancer which can be diagnosed by histology and immunohistochemical staining result. The majority of patients presented with muscle invasion and had a poor survival despite aggressive treatment.

Secondary tumors of the bladder: A survival outcome study

The urinary bladder may be involved by a variety of secondary tumors that originate from other organs. Bladder secondary tumors are rare and may be mistaken as bladder primary tumors because of their overlapping morphologic features. To avoid the diagnostic pitfalls, we analyzed the clinicopathologic features of bladder secondary tumors in a large cohort of patients. Our patient cohort consisted of 45 females and 38 males with a mean age of 58.7 ± 15.4 years (range 10-87 years). The tumors involved the bladder via direct extension from adjacent organs (n = 42) and distant metastasis (n = 41). In females, the majority of secondary tumors originated from the gynecologic tract (n = 25), and other common origins included the colon/rectum (n = 5) and breast (n = 4). In males, the most common origin was the prostate (n = 18), followed by the colon/rectum (n = 4) and kidney (n = 3). 75.9% of the secondary tumors were adenocarcinoma (n = 63), and other common tumor types included sarcoma (n = 6), squamous cell carcinoma (n = 5), melanoma (n = 4), and neuroendocrine carcinoma (n = 3). 67.5% of patients (n = 56) died of the disease with a median overall survival of 23 months from the time of secondary involvement of the bladder. Patients with secondary tumors via direct extension had a median survival time of 20 months, which was not significantly different from that for patients with secondary involvement via distant metastasis (24 months) (p = 0.83). Median survival in cases with prostate primary was 20 months as compared to 23 months for all other tumor types (p = 0.68). The majority of secondary tumors are composed of adenocarcinoma, which highlights the importance of differentiating primary from secondary involvement in bladder adenocarcinoma. Regardless of the origin, bladder secondary tumors are associated with a poor prognosis.

Diagnostic and prognostic roles of CK20 in the pathology of urothelial lesions. A systematic review

Cytokeratin 20 (CK20) is one of the most common immunohistochemical markers in the routine practice of a pathology lab, as biopsies from the urinary tract encompass a wide spectrum of lesions which may pose issues in their detection and classification. In this review, we aim to outline the diagnostic accuracy and prognostic value of CK20 in flat urothelial lesions, papillary non-invasive and invasive urothelial carcinoma, molecular subgroups and variant histology, and we briefly discuss its limitations and potential pitfalls.

Non-urothelial carcinomas of the bladder

Non-urothelial carcinomas involving the bladder are uncommon and often diagnostically challenging. These carcinomas may show squamous, adenocarcinomatous or neuroendocrine features, with immunohistochemical stains aiding the diagnosis in only a subset of cases. The clinical history in non-urothelial bladder carcinomas is important, given that the differential diagnosis often includes secondary involvement of the bladder by direct extension or metastasis from carcinomas at other sites. This paper will review non-urothelial carcinomas in each of these three morphological categories, emphasising recent changes in diagnostic grouping and challenges in the histopathological diagnosis. Review of bladder cancers with squamous morphology will include discussion of conventional squamous cell carcinoma and verrucous carcinoma and their distinction from urothelial carcinoma with extensive squamous differentiation. Bladder carcinomas with adenocarcinomatous change will include primary bladder adenocarcinoma, urachal adenocarcinoma and tumours of Müllerian type. Finally, neuroendocrine neoplasms of the bladder, including well-differentiated neuroendocrine tumour and neuroendocrine carcinomas, will be discussed. Associated surface findings, risk factors and prognostic features will be described.

Non-muscle-invasive clear cell carcinoma of the urinary bladder: Is cystectomy necessary?

We report the clinical presentation, histological findings and management of a 49-year-old female patient with non-muscle-invasive clear cell carcinoma of the urinary bladder. In the literature, there are only seven such case reports. We feel that transurethral resection of the bladder tumour followed by close cystoscopy surveillance is a suitable management for non-muscle-invasive clear cell carcinoma of the urinary bladder.

Clear cell adenocarcinoma of the prostatic urethra: A case report

Introduction

Clear cell adenocarcinoma of the prostatic urethra in men is an extremely rare disease, with only eight case reports published.

Case presentation

A 56‐year‐old man visited our hospital for gross hematuria. Urinary cytology detected class V, cystoscopy showed no abnormal findings, and contrast‐enhanced computed tomography also showed no abnormal findings in his upper urinary tract except for a low‐enhancement lesion on his left prostate lobe. Magnetic resonance imaging revealed a cystic lesion surrounding the prostate that was suspected of being urethral or prostate cancer, so transurethral resection was performed. A papillary tumor was detected at the prostatic urethra, and after resecting this tumor, a cavity showing multiple tumors was observed. The final pathological diagnosis was clear cell adenocarcinoma. Laparoscopic radical cystectomy and urethrectomy were thus performed. The pathological diagnosis was the same as at the primary tumor site.

Conclusion

We herein report a case of clear cell adenocarcinoma of the prostatic urethra.

High-dose-rate brachytherapy - a novel treatment approach for primary clear cell adenocarcinoma of male urethra

The incidence of male urethral cancer is rare with age preponderance of 50 to 60 years. The standard management approach is surgery. Here, we present a novel treatment approach for male urethral cancer. Thirty-six year old male, case of primary clear cell adenocarcinoma of urethra who refused surgery, underwent cystoscopic assisted intraluminal HDR brachytherapy. Patient received a dose of 36 Gy in 9 fractions (4 Gy per fraction) followed by a boost of 24 Gy in 6 fractions. At 11 months post treatment, disease is well controlled with no post treatment toxicity so far. Intraluminal brachytherapy seems to be an effective novel treatment for male urethral cancer.

Clear cell adenocarcinoma of the urethra: review of the literature

Background. Clear cell adenocarcinoma of the urethra (CCAU) is extremely rare and a number of clinicians may be unfamiliar with its diagnosis and biological behaviour. Aims. To review the literature on CCAU. Methods. Various internet databases were used. Results/Literature Review. (i) CCAU occurs in adults and in women in the great majority of cases. (ii) It has a particular association with urethral diverticulum, which has been present in 56% of the patients; is indistinguishable from clear cell adenocarcinoma of the female genital tract but is not associated with endometriosis; and probably does not arise by malignant transformation of nephrogenic adenoma. (iii) It is usually, readily distinguished from nephrogenic adenoma because of greater cytological a-typicality and mitotic activity and does not stain for prostate-specific antigen or prostatic acid phosphatase. (iv) It has been treated by anterior exenteration in women and cystoprostatectomy in men and at times by radiotherapy; chemotherapy has rarely been given. (v) CCAU is aggressive with low 5-year survival rates. (vi) There is no consensus opinion of treatment options that would improve the prognosis. Conclusions. Few cases of CCAU have been reported. Urologists, gynaecologists, pathologists, and oncologists should report cases of CCAU they encounter and enter them into a multicentric trial to determine the best treatment options that would improve the prognosis.

Primary Clear Cell Carcinoma of the Urinary Bladder

Primary clear cell carcinoma of the urinary bladder (PCCUB) is rare. Literature review has revealed 47 cases of PCCUB which commonly affects women. The histogenesis of PCCUB is not certain and Müllerian origin and urotheilal origin have been postulated. The microscopic characteristics of PCCUB include cells with abundant clear cytoplasm, arranged in a solid, glandular, tubulocystic, or papillary pattern. The cells may be flat or cuboidal with abundant clear eosinophilic cytoplasm. Hobnailing may be evident. PCCUB, on immunohistochemistry, stain positively with pan-cytokeratin, cytokeratin 7, and CA 125. PCCUB may manifest with visible haematuria, lower urinary tract symptoms, and discharge. There is no consensus opinion regarding the best treatment option for PCCUBs and patient outcomes are not very clear. Surgery has been the adopted treatment of choice. Differential diagnoses of PCCUB include nephrogenic metaplasia, urothelial carcinoma with clear cell cytoplasm, diffuse large B-cell lymphoma, and metastatic clear cell carcinoma with the primary originating elsewhere. Conclusions. A thorough radiological imaging assessment is required in cases of PCCUB to exclude a primary tumour elsewhere. Urologists and oncologists should report cases of PCCUB they encounter and should enter them into a multicentric trial to ascertain the best management option.

Primary urethral clear-cell adenocarcinoma: comprehensive analysis by surgical pathology, cytopathology, and next-generation sequencing

Primary clear-cell adenocarcinoma of the urethra, a rare tumor that histomorphologically resembles clear-cell carcinoma of the female genital tract, occurs predominantly in women and is associated with a relatively poor prognosis. The histogenesis of this rare urethral neoplasm has not been completely resolved, but it is thought to arise from either müllerian rests or metaplastic urothelium. Herein, we present comprehensive surgical pathological and cytopathological findings from a patient with primary urethral clear-cell adenocarcinoma and describe next-generation sequencing results for this patient's unique tumor-the first such reported characterization of molecular aberrations in urethral clear-cell adenocarcinoma at the transcriptomic and genomic levels. Transcriptome analysis revealed novel gene fusion candidates, including ANKRD28-FNDC3B. Whole-exome analysis demonstrated focal copy number loss at the SMAD4 and ARID2 loci and 38 somatic mutations, including a truncating mutation in ATM and a novel nonsynonymous mutation in ALK.

Utility of α-methylacyl-coenzyme-A racemase (p504s) immunohistochemistry in distinguishing endometrial clear cell carcinomas from serous and endometrioid carcinomas

The expression of α-methylacyl-coenzyme-A racemase (AMACR) has previously been reported in 75% to 100% of urethral/bladder clear cell carcinomas, tumors that are known to display broad phenotypic overlap with their identically named müllerian counterparts. Herein, we assess the utility of AMACR in distinguishing endometrial clear cell carcinomas (CCCs) from endometrial serous carcinomas (ESCs) and endometrial endometrioid carcinomas (EECs). A total of 111 endometrial carcinomas in a tissue microarray, including 49 CCCs, 13 ESCs, and 49 EECs, were assessed for AMACR immunoreactivity, with results scored semiquantitatively (scores 0, 1+, 2+, 3+ for 0%, 1%-5%, 6%-50%, >50% immunoreactive cells, respectively). Fifty (45%) of the 111 carcinomas were AMACR positive, with the following score distribution: CCC: 0 (n = 12), 1+ (n = 12), 2+ (n = 3), 3+ (n = 22); EEC: 0 (n = 38), 1+ (n = 4), 2+ (n = 4), 3+ (n = 3); ESC: 0 (n = 11), 1+ (n = 1), 2+ (n = 0), 3+ (n = 1). AMACR expression was significantly more frequent in CCC (75%) than in ESC (15%) or EEC (22%); P < .0001. The sensitivity and specificity of AMACR expression in classifying a carcinoma as CCC were 0.75 (95% confidence interval [CI], 0.61-0.86) and 0.79 (95% CI, 0.66-0.88), respectively, with an odds ratio of 11.62 (95% CI, 5-28; P < .001) and an area under the curve of 0.79 (95% CI, 0.68-0.88). These findings indicate that AMACR expression is strongly associated with CCC and displays a relatively robust diagnostic test performance. However, its practical utility may be limited by the focal nature of its expression in 32% of the AMACR-positive CCC cases as well as its expression in 15% to 22% of the non-CCC histotypes.

Cytologic findings of clear cell adenocarcinoma of the urethra: a case report

Clear cell adenocarcinoma of the urethra is a rare disease entity with an uncertain histogenesis. Here, we present a case of primary clear cell adenocarcinoma of the female urethra with its cytological findings. A 54-year-old woman presented with a painless gross hematuria lasting 3 months. On vaginal sonography, there was a sausage-like, elongated mass in the urethra, measuring 3.8×4.3 cm. The voided urine cytology revealed small clusters of rounded or papillary cells. The necrotic debris and inflammatory cells were present within some clusters of tumor cells. These tumor cells were enlarged and had abundant clear or granular cytoplasm with cytoplasmic vacuoles. The nucleus was granular and contained vesicular chromatin with prominent nucleoli. The hobnail cells and hyaline globules were also present as in a histologic section. The histologic findings were compatible with clear cell adenocarcinoma. The tumor showed distinctive cytological features. Cytologically, however, it is necessary to make a differential diagnosis from other adenocarcinoma or high-grade urothelial carcinoma.

Nephrogenic Adenoma of the Urinary Tract

Nephrogenic adenoma (NA) is an uncommon and intriguing lesion in the urinary tract. The pathogenesis of NA is not entirely clear. NA was considered to be a metaplastic process of the urothelium in response to chronic irritation of the urinary tract. However, recent evidence has shown that NA is not a metaplastic lesion but rather a proliferation of exfoliated and implanted renal epithelial cells in the urinary tract. Histologically, NAs exhibit, singly or in combination, tubules, small papillae, and microcystic structures lined by cells with little cytological atypia and focal hobnail changes. Solid formations and compressed spindled cells within a fibromyxoid background are rarely observed. Differential diagnosis includes, but is not limited to, malignant neoplasms occurring at the same sites, in particular urothelial carcinoma with deceptively bland morphology (with small tubules, microcystic and nested variants), prostatic adenocarcinoma, and clear cell adenocarcinoma. Immunohistochemical studies with antibodies targeting members of the paired box gene family (PAX2 and/or PAX8) in NAs may be helpful in the differential diagnosis of urothelial lesions and prostatic adenocarcinoma. NAs are most likely to be confused with clear cell adenocarcinoma, especially in small biopsy specimens. This is confounded by both lesions being frequently positive for PAX2, PAX8, and CK7 and not infrequently positive for p504S (α-methylacyl-CoA-racemase, AMACR) by immunohistochemistry. Recognition of its characteristic morphological patterns and awareness of its unusual architectural and cytological features are important in making the diagnosis of NA and distinguishing this lesion from its mimickers.

Primary clear cell adenocarcinoma of the bladder with recurrence: a case report and literature review

Clear cell carcinoma of the bladder is a rare tumor of the bladder. There are few reports available on this rare disease, and no cases with recurrence were reported. Here we present a case of 68-year-old woman with primary clear cell carcinoma of the bladder, who underwent repeat TUR-BT and tumor recurrence. We also reviewed the previous treatments and prognoses in previous case reports and evaluate the proper treatment for this disease. Once the diagnosis is determined, the radical surgery should be recommended. The recurrence is not prevented based on post-TUR intravesical therapy.

Clear cell adenocarcinoma of urinary bladder: A case report and review

Clear cell carcinoma is an uncommon but distinct variant of urinary bladder carcinoma histologically resembling the neoplasm in the female genital tract. The histogenesis of this neoplasm is uncertain. The clinicopathologic and histologic features are suggestive of a mullerian origin in some tumors, while some believe it to be glandular differentiation of urothelium or a unique vesicular adenocarcinoma of non-mullerian origin.[1] We present a case of clear cell adenocarcinoma in a 74-year-old woman with review of literature along with its differential diagnosis.

Hepatocyte nuclear factor-1β expression in clear cell adenocarcinomas of the bladder and urethra: diagnostic utility and implications for histogenesis

The histogenesis of clear cell adenocarcinoma of the bladder/urethra is uncertain. Hepatocyte nuclear factor-1β is a homeodomain protein that has been reported to be frequently overexpressed in ovarian clear cell adenocarcinoma in comparison with rare or no expression in other types of epithelial ovarian tumors. We assessed the expression of hepatocyte nuclear factor-1β in a series of 18 clear cell adenocarcinomas of the bladder and urethra and compared it with that of invasive high-grade transitional/urothelial carcinoma (n = 35); adenocarcinomas of the bladder, urethra, and paraurethral glands (n = 21); as well as nephrogenic adenomas of the bladder (n = 8). Staining intensity and extent were evaluated using a 4-tiered grading system (0-3). A case was considered positive for hepatocyte nuclear factor-1β if 10% or more of tumor cells showed at least weak nuclear staining or if any moderate or strong nuclear staining was observed. All 18 clear cell adenocarcinomas exhibited nuclear staining in at least 50% of tumor cells (16 strong, 1 moderate, and 1 weak with focal strong nuclear staining) in comparison with positive nuclear staining (moderate) in 1 of 21 bladder adenocarcinoma, 1 of 35 invasive high-grade transitional/urothelial carcinoma (weak to moderate staining), and 2 of 8 nephrogenic adenomas (1 weak and 1 moderate to strong staining). We concluded that hepatocyte nuclear factor-1β is a useful marker in differentiating clear cell adenocarcinomas of the bladder/urethra from invasive high-grade transitional/urothelial carcinoma and other types of bladder adenocarcinomas and to a lesser extent from nephrogenic adenomas. Hepatocyte nuclear factor-1β is of no diagnostic utility in discriminating primary bladder/urethral clear cell adenocarcinomas from metastatic clear cell adenocarcinomas of the female genital tract to the bladder/urethra. From a histogenesis standpoint, although the expression of hepatocyte nuclear factor-1β in both gynecologic and urologic tract clear cell adenocarcinomas may point to a Müllerian derivation/differentiation, this immunohistochemical evidence is insufficient to completely exclude an urothelial association.

Immunohistochemical diagnosis of renal neoplasms

CONTEXT

Histologic diagnosis of renal neoplasm is usually straightforward by routine light microscopy. However, immunomarkers may be essential in several contexts, including differentiating renal from nonrenal neoplasms, subtyping of renal cell carcinoma (RCC), and diagnosing rare types of renal neoplasms or metastatic RCC in small biopsy specimens.

OBJECTIVE

To provide a comprehensive review of the diagnostic utility of immunomarkers for renal neoplasms.

DESIGN

This review is based on published literature and personal experience.

CONCLUSIONS

The following markers may have diagnostic utility in various diagnostic contexts: cytokeratins, vimentin, α-methylacyl coenzyme A racemase, carbonic anhydrase IX, PAX2, PAX8, RCC marker, CD10, E-cadherin, kidney-specific cadherin, parvalbumin, claudin-7, claudin-8, S100A1, CD82, CD117, TFE3, thrombomodulin, uroplakin III, p63, and S100P. Cytokeratins are uniformly expressed by RCC, albeit in a somewhat limited amount in some subtypes, requiring broad-spectrum anti-CK antibodies, including both low- and high-molecular-weight cytokeratins. PAX2 and PAX8 are sensitive and relatively specific markers for renal neoplasm, regardless of subtype. CD10 and RCC marker are sensitive to renal cell neoplasms derived from proximal tubules, including clear cell and papillary RCCs. Kidney-specific cadherin, parvalbumin, claudin-7, and claudin-8 are sensitive markers for renal neoplasms from distal portions of the nephron, including chromophobe RCC and oncocytoma. CK7 and α-methylacyl coenzyme A racemase are sensitive markers for papillary RCC; TFE3 expression is essential in confirming the diagnosis of Xp11 translocation RCC. The potentially difficult differential diagnosis between chromophobe RCC and oncocytoma may be facilitated by S100A1 and CD82. Thrombomodulin, uroplakin III, p63, and S100P are useful markers for urothelial carcinoma. Together with high-molecular-weight cytokeratins, PAX2, and PAX8, they can help differentiate renal pelvic urothelial carcinoma from collecting duct RCC. A sensitive marker for sarcomatoid RCC is still not available. Immunomarkers are most often used for diagnosing metastatic RCC. Compared with primary RCC, expression of the above-mentioned markers is often less frequent and less diffuse in the metastatic setting. Recognizing the variable sensitivity and specificity of these markers, it is important to include at least CD10, RCC marker, PAX2, and PAX8 in the diagnostic panel.

The use of immunohistochemistry in the diagnosis of metastatic clear cell renal cell carcinoma: a review of PAX-8, PAX-2, hKIM-1, RCCma, and CD10

The diagnosis of metastatic clear cell renal cell carcinoma may be difficult in some cases, particularly in the small image-guided biopsies that are becoming more common. As targeted therapies for renal cell carcinoma are now standard treatment, the recognition and diagnosis of renal cell carcinoma has become even more critical. Many adjunctive immunohistochemical markers of renal epithelial lineage such as CD10 and RCCma have been proposed as aids in the diagnosis of metastatic renal cell carcinoma, but low specificities often limit their utility. More recently described markers (PAX-2, PAX-8, human kidney injury molecule-1, hepatocyte nuclear factor-1-β, and carbonic anhydrase-IX) offer the potential for greater sensitivity and specificity in this diagnostic setting; however, knowledge of their expected staining in other neoplasms and tissues is critical for appropriate use. In this review, we discuss the most widely used immunohistochemical markers of renal lineage with an emphasis on their sensitivity and specificity for metastatic clear cell renal cell carcinoma. Subsequently, we present a variety of organ-specific differential diagnostic scenarios in which metastatic clear cell renal cell carcinoma might be considered and we propose immunopanels for use in each situation.

Histological variants of urothelial carcinoma: diagnostic, therapeutic and prognostic implications

It is well established that invasive urothelial carcinoma, involving the urinary bladder and renal pelvis, has marked propensity for divergent differentiation. In recent years, several 'variant' morphologies have been described and most have been recognized in the 2004 World Health Organization Classification. These histological variants of urothelial carcinoma have clinical significance at various levels, including diagnostic, that is, awareness of the morphological variant is essential in order to avoid diagnostic misinterpretations; prognostic for patient risk stratification; and therapeutic, where a diagnostic assignment of a particular variant may be associated with the administration of a therapy distinctive from that used in conventional invasive urothelial carcinoma. The diagnoses of micropapillary urothelial carcinoma, small-cell carcinoma, lymphoepithelioma-like carcinoma and sarcomatoid carcinoma are prime examples where treatment protocols may be different than the usual muscle-invasive bladder cancer. This review discusses the variants of urothelial carcinoma, outlining for each the diagnostic features, differential diagnostic considerations and the clinical significance.