Pseudoneoplastic mimics of prostate and bladder carcinomas

Navigating management of localized prostate cancer in the geriatric population

Prostate cancer (PCa) is highly prevalent among aging men and a significant contributor to global mortality. Balancing early detection and treatment of "clinically significant" disease with avoiding over-detection and overtreatment of slow-growing tumors is challenging, especially for elderly patients with competing health risks and potentially aggressive disease phenotypes. This review emphasizes the importance of individualized approaches for diagnosing and treating PCa in geriatric patients. Active surveillance and watchful waiting are common strategies, while surgical interventions are less frequent but considered based on comorbidities, disease risk, and patient preferences. Radiotherapy, often combined with androgen deprivation therapy, is typical for higher-risk cases, and focal therapy is emerging to reduce morbidity. An inclusive approach combining advanced diagnostics, life expectancy considerations, and minimally invasive interventions can improve decision-making. Integrating multidisciplinary strategies with better risk stratification and less invasive options can significantly enhance care and outcomes for elderly patients with significant PCa.

Utility of AMACR immunohistochemical staining in differentiating Arias-Stella reaction from clear cell carcinoma of ovary and endometrium

BACKGROUND

The Arias-Stella reaction is a hormone-related atypical endometrial change characterized by cytomegaly, nuclear enlargement, and hyperchromasia of endometrial glands; typically associated with intrauterine or extrauterine pregnancies or with gestational trophoblastic disease. Although differentiating the Arias-Stella reaction (ASR) from clear cell carcinoma (CCC) of the endometrium is usually straightforward, but differentiating ASR might be difficult if it occurs outside the setting of pregnancy, in extra-uterine sites or in older patients. The aim of this study was to determine whether P504S/Alpha Methyacyl CoA racemase (AMACR) immunohistochemical (IHC) staining can be used to differentiate ASR from CCC.

METHODS

Fifty endometrial ASR and 57 CCC samples were assessed by IHC staining with antibody for AMACR. The immunoreactive score (IRS) was based on total intensity score (no staining to strong scored as 0-3) + percentage score (0-100% categorized as 0-3) ranged from 0 to 6. Positive expression was considered as a total IRS exceeding 2.

RESULTS

The mean age of the patients in the ASR was significantly lower than that of CCC (33.34 ± 6.36 and 57.81 ± 11.64 years old, respectively, p < 0.001). The overall AMACR staining score was significantly higher among CCC compared to ASR groups (p = 0.003). The positive and negative predictive values for AMACR expression in detecting CCC from ASR were 81.1% and 57%, respectively.

CONCLUSION

IHC staining for AMACR can be helpful and a member of discriminatory IHC panel when clinical or histologic features cannot facilitate the differential diagnosis between ASR versus CCC.

Tumour-like lesions of the urinary bladder

There are a number of benign epithelial proliferations in the bladder that may be difficult to distinguish from carcinomas, including urothelial carcinoma and its variants, squamous cell carcinoma and adenocarcinoma. If misdiagnosed, there is the potential for over treatment, with its attendant risk of complications, as well as errors relating to prognostic assessment. In the case of the misdiagnosis of high grade proliferative lesions that mimic invasive carcinoma, unnecessary radical surgery, chemotherapy and radiotherapy may result. Similarly, the misdiagnosis of lesions that have the appearance of low grade carcinoma can prompt a lifetime of radiological investigation and cystoscopies. In this review, we discuss a variety of entities that may be diagnostically challenging and emphasise the importance of identifying key morphological features that have diagnostic utility. We also highlight the importance of relevant clinical information and the clinical settings in which these lesions may occur. In this review we have divided the lesions on the basis of morphology in order to facilitate discussion relating to the differential diagnosis. The architectural patterns we discuss include papillary lesions (polypoid/papillary cystitis and papillary urothelial hyperplasia), pseudocarcinomatous proliferations (pseudocarcinomatous urothelial hyperplasia, florid proliferation of von Brunn nests and fibroepithelial polyps), glandular lesions (intestinal metaplasia and müllerianosis) and lesions with several different patterns (prostatic type urethral polyps and nephrogenic adenoma or metaplasia).

Large-Gland Proliferations of the Prostate

Large-gland proliferations of the prostate have gained considerable attention in the past decade. The differential diagnosis is quite broad but can be refined using histologic criteria and, sometimes, immunostains. Pathologists have come to realize that cribriform and intraductal as well as ductal carcinomas are particularly aggressive patterns, and should name them in diagnostic reporting when present.

Evolving concepts and use of immunohistochemical biomarkers in flat non-neoplastic urothelial lesions: WHO 2016 classification update with diagnostic algorithm

CONTEXT

The classification of flat non-neoplastic urothelial lesions has been evolved through the years in the attempt to better define a spectrum of morphologic entities with somewhat overlapping features. Differentiating these lesions is important because of differences in patient management and clinical outcome. Materials and methods and objective: A systematic review of the literature has been carried out in order to (1) assess the most striking clinical features of each lesion and (2) identify those morphological traits and immunophenotypical markers which may aid in the differential diagnosis.

RESULTS AND CONCLUSION

Our results point out the importance of a proper definition of flat non-neoplastic urothelial lesions in order to predict clinical behaviour and allow tailored patient management; therefore, we attempted to construct a novel and "easy to use" algorithm for a clear, standardized and evidence-based pathological diagnosis.

Benign mimics of prostatic adenocarcinoma

Benign mimics present either as common challenges in daily routine practice or may cause diagnostic dilemmas because some are less commonly seen and one may be less familiar in recognizing them. There are a multitude of mimics of prostatic adenocarcinoma, which may represent normal gland structures, benign proliferations, atrophic lesions, hyperplastic or metaplastic changes, and inflammatory processes. Some of them are preferentially found in certain anatomic areas of the prostate, either confined to the prostate, or outside of the gland. Various benign mimics of prostatic carcinoma may be also evaluated based on their morphologic similarity to Gleason patterns 3-5 of prostatic adenocarcinoma. Most of the mimics are easily recognizable in larger specimens, such as TUR of the prostate or radical prostatectomy specimens, but they may pose diagnostic problems when the evaluation is done on limited tissue, such as needle-core biopsies or if prostate specimens are infrequently encountered in practice. Therefore, before signing out a report with a diagnosis of prostatic carcinoma, pathologists should carefully consider and rule out the various benign lesions that may mimic carcinoma. This is particularly relevant in the current prostate biopsy practice which relies on using extended biopsy core templates. The awareness and familiarity with the characteristic features of the mimics and judicial use of additional ancillary tests, including immunohistochemistry can prevent overdiagnosis and false-positive interpretation. This review provides a contemporary update on the broad spectrum of the benign prostatic lesions that can mimic prostate adenocarcinoma, outlines their key morphologic and immunohistochemical diagnostic features, and provides a diagnostic, pattern-based approach in establishing a correct diagnosis and distinguishing them reliably from prostatic adenocarcinoma.

Minimal (Limited) Pseudohyperplastic Prostatic Adenocarcinoma in Needle Prostatic Biopsy

Background. Study of minimum adenocarcinoma has been done almost exclusively on conventional acinar adenocarcinoma. Pseudohyperplastic adenocarcinoma can be confused with benign lesions because of its well-differentiated appearance and has not been studied when the biopsy shows few malignant glands (limited carcinoma). Methods. We reviewed 94 pseudohyperplastic adenocarcinomas diagnosed in prostatic biopsies for a period of 12 years and selected those measuring less than 1 mm or involving less than 5% of the biopsied tissue. We also reviewed 200 consecutive consultations. Results. Four (4.2%) of the 94 cases were limited pseudohyperplastic adenocarcinomas, and 3 were from consultations. Three of them were mistaken for hyperplastic nodules, prostatic adenosis, or prostatic intraepithelial neoplasm. The number of glands varied between 6 and 50 (average 23). Three nodular histological patterns were identified—nodular, adenosis-like, and pseudohyperplastic carcinoma resembling prostatic intraepithelial neoplasia. The diagnosis of adenocarcinoma was not related to the number of neoplastic glands. Histological criteria that were useful included: crowded medium to large glands, papillary infoldings, branching glands, straight luminal borders, hyperchromatic nuclei, nucleomegaly, and apparent nucleoli. Areas of transition to conventional acinar adenocarcinoma were useful in recognizing four of these neoplasms, but were barely apparent in 2 of them. Hyperchromatic nuclei were found in all cases, whereas apparent nucleoli and nucleomegaly were only present in 4. Conclusions. The architectural and cytological criteria for limited acinar adenocarcinoma are only partially useful in interpreting minimum pseudohyperplastic adenocarcinomas. Knowledge of the criteria for malignancy in both neoplasms is important in order to avoid underdiagnosis of malignancy.

Immunohistochemistry in the workup of prostate biopsies: Frequency, variation and appropriateness of use among pathologists practicing at an academic center

OBJECTIVES

We studied the frequency, inter-pathologist variation, appropriateness and utility of immunohistochemistry (IHC) performed on prostate biopsies (PB) to determine the significance of foci of suspicious glands/atypical small acinar proliferations (ASAP).

METHODS

We calculated the rate of IHC use and diagnostic rate of ASAP and adenocarcinoma in PB from 01/01/2008 to 06/30/2015 for individual pathologists working in a tertiary academic institution, and correlated them with the pathologists' experience, subspecialization and PB volume with the aim of determining the interpathologist variation and appropriateness of use of IHC according to recently published recommendations, and the usefulness of IHC to resolve foci of ASAP as either benign or adenocarcinoma.

RESULTS

IHC was used in 966/2652 (36.4%, 95% CI 33.4-39.4%) PB cases and 1915 of 16,359 (11.7%, 95% CI 11.2%-12.2%) of PB blocks and allowed definitive diagnosis of either benign or malignant in 75.8% (95% CI 73.9-77.7%) of blocks. By pathologist, IHC use rates varied more than twofold (22.8-50.5%); higher use was found for pathologists with genitourinary pathology specialization, higher PB volume and more experience, and correlated with higher rates of both ASAP and adenocarcinoma diagnoses. The use of IHC stains was considered appropriate in 822/966 (85.1%, 95% CI 82.9-87.4%) cases.

CONCLUSIONS

Despite the fact that the use of IHC stains was considered useful and deemed appropriate in the majority of cases, it showed wide variation between pathologists, suggesting monitoring of IHC use rates may be useful to standardize its use.

Low grade urothelial carcinoma mimicking basal cell hyperplasia and transitional metaplasia in needle prostate biopsy

PURPOSE

The vast majority of urothelial carcinomas infiltrating the bladder are consistente with high-grade tumors that can be easily recognized as malignant in needle prostatic biopsies. In contrast, the histological changes of low-grade urothelial carcinomas in this kind of biopsy have not been studied.

MATERIALS AND METHODS

We describe the clinicopathologic features of two patients with low-grade bladder carcinomas infiltrating the prostate. They reported dysuria and hematuria. Both had a slight elevation of the prostate specific antigen and induration of the prostatic lobes. Needle biopsies were performed. At endoscopy bladder tumors were found in both cases.

RESULTS

Both biopsies showed nests of basophilic cells and cells with perinuclear clearing and slight atypia infiltrating acini and small prostatic ducts. The stroma exhibited extensive desmoplasia and chronic inflammation. The original diagnosis was basal cell hyperplasia and transitional metaplasia. The bladder tumors also showed low-grade urothelial carcinoma. In one case, the neoplasm infiltrated the lamina propria, and in another, the muscle layer. In both, a transurethral resection was performed for obstructive urinary symptoms. The neoplasms were positive for high molecular weight keratin (34BetaE12) and thrombomodulin. No metastases were found in either of the patients, and one of them has survived for five years.

CONCLUSIONS

The diagnosis of low-grade urothelial carcinoma in prostate needle biopsies is difficult and may simulate benign prostate lesions including basal cell hyperplasia and urothelial metaplasia. It is crucial to recognize low-grade urothelial carcinoma in needle biopsies because only an early diagnosis and aggressive treatment can improve the prognosis for these patients.

The pathology of urinary bladder lesions with an inverted growth pattern

Inverted lesions in the urinary bladder have been the source of some difficulty in urological pathology. The two common ones are von Brunn's nests and cystitis cystic/cystitis glandularis, which are considered normal variants of urothelium. Apart from them, a number of other rare urothelial lesions with inverted growth pattern occur in the urinary bladder. Some of them are only reactive conditions, just as pseudocarcinomatous hyperplasia. Some are benign tumors, namely inverted papilloma. Whereas others are malignant neoplasms, including inverted papillary urothelial neoplasm of low malignant potential (PUNLMP), non-invasive inverted papillary urothelial carcinoma (low-grade and high-grade), and invasive urothelial carcinoma (inverted, nested and big nested variants). Because of the overlapping morphological features of all the inverted lesions mentioned above, even between high-grade invasive carcinoma and pseudocarcinomatous hyperplasia which are only a kind of reactive conditions, it is very important for the surgical pathologist to recognize and be familiar with these inverted lesions in urinary bladder. In this article, we review these spectrums of inverted lesions of the urinary bladder. Emphasis is placed on histogenesis, morphology, differential diagnosis of these lesions, and the pathologic grading of the non-invasive inverted neoplasms, such as inverted papilloma, inverted PUNLMP, non-invasive inverted papillary urothelial carcinoma with low-grade, and non-invasive inverted papillary urothelial carcinoma with high-grade.

Diagnostic Difficulties With Atrophy, Atypical Adenomatous Hyperplasia, and Atypical Small Acinar Proliferation: A Systematic Review of Current Literature

Prostate cancer is the second leading cause of cancer death in men, behind only lung cancer. In some cases, the proper diagnosis of prostatic neoplasia can be challenging, and the differential diagnosis includes atypical nonmalignant lesions such as atrophy, atypical adenomatous hyperplasia (AAH), and atypical small acinar proliferation (ASAP). Atrophy and AAH have a benign clinical outcome, and if detected on needle biopsy or transurethral resection of the prostate, clinical follow-up seems appropriate. In contrast, ASAP cannot be determined to be benign or malignant. In clinical practice, the diagnosis of ASAP is an indication for repeat biopsy because the chance of finding prostate adenocarcinoma is even greater than that with an earlier diagnosis of high-grade prostatic intraepithelial neoplasia. Malignant lesions require more restrictive treatment; therefore, differentiation among atrophy, AAH, ASAP, and adenocarcinoma is essential. We performed a systematic review of the current data allow to the creation of a diagnostic algorithm for atrophy, AAH, ASAP, and adenocarcinoma. We propose an algorithm that covers the practical issues related to interpretation of the biopsy findings and how to proceed further.

Basal cell hyperplasia (BCH) versus high grade prostatic intraepithelial neoplasia (HGPIN) in tiny prostatic needle biopsies: Unusual diagnostic dilemma

BACKGROUND

Histopathological differentiation between BCH and HGPIN in prostatic needle biopsies is a diagnostic challenge. The gold standard for detection of HGPIN and BCH is histopathological examination; however subjectivity in interpretation and tiny volume of obtained tissue hamper reliable diagnosis.

AIMS

The aim of this study was to assess usefulness of using the p63 and p504s to solve this problem. Although the use of p63 and p504s is now well established in differentiation between preneoplastic and neoplastic prostatic lesions, their usefulness in tiny tissue material is, however, not fully studied.

METHODS

The study included a spectrum of 30 prostatic needle biopsies (5 BCH, 10 HGPIN, 10 indefinite luminal proliferations where BCH and HGPIN could not be distinguished from each other and 5 adenocarcinomas). H&E stained sections were examined for histopathological features. Other sections were stained immunohistochemically with p63 and p504s.

RESULTS

The mean age of patients was 69 (SD=7.6) years. PSA range was 1.3-2.7 ng/ml. Ultrasongraphic findings were unremarkable. All BCH showed p504s-/p63+ pattern, All HGPIN had p504s+/p63+ pattern while carcinomas were p504s+/p63-. After immunostaining combined with histopathological features; the 10 indefinite specimens could be diagnosed as 4 BCH and 6 HGPIN. The article explains how applying this staining pattern on the challenging specimens, combined with histopathological features, can be helpful in proper identification of prostatic proliferations.

Histopathological spectrum of 364 prostatic specimens including immunohistochemistry with special reference to grey zone lesions

Purpose:

Prostatic lesions on routine staining sometimes cause a diagnostic dilemma, especially when malignant tissue is limited and is mixed with benign prostatic glands or because of the presence of benign mimickers of carcinoma. The application of immunohistochemistry contributes a valuable differential diagnosis. This study aimed to evaluate a complete spectrum of various prostatic lesions and to supplement the histopathological diagnosis with immunohistochemistry in suspicious or atypical cases.

Methods:

A total of 364 consecutive prostatic specimens were evaluated. Routine hematoxylin and eosin staining and immunohistochemical staining against 34βE12 cytokeratin and proliferative marker (alpha-methylacyl-CoA-racemase, AMACR) were performed by use of the peroxidase antiperoxidase method.

Results:

Benign prostatic hyperplasia was the most frequent finding and involved 285 patients (78.3%). Prostatitis (majority nonspecific) formed the predominant subgroup in nonneoplastic lesions (n=119, 32.7%). The incidence of carcinoma was low (n=73, 20.1%). Of the 26 atypical or suspicious cases, 18 cases were positive for high molecular weight cytokeratin (high molecular weight cytokeratin, HMWCK) only, 4 cases were positive for AMACR only, and 4 cases showed positivity for both HMWCK and AMACR.

Conclusions:

Biopsy remains the gold standard. However, as an adjunct to biopsy, proliferative markers and basal cell markers have value for resolving suspicious or atypical cases.

Paragangliomas: update on differential diagnostic considerations, composite tumors, and recent genetic developments

Recent developments in molecular genetics have expanded the spectrum of disorders associated with pheochromocytomas (PCCs) and extra-adrenal paragangliomas (PGLs) and have increased the roles of pathologists in helping to guide patient care. At least 30% of these tumors are now known to be hereditary, and germline mutations of at least 10 genes are known to cause the tumors to develop. Genotype-phenotype correlations have been identified, including differences in tumor distribution, catecholamine production, and risk of metastasis, and types of tumors not previously associated with PCC/PGL are now considered in the spectrum of hereditary disease. Important new findings are that mutations of succinate dehydrogenase genes SDHA, SDHB, SDHC, SDHD, and SDHAF2 (collectively "SDHx") are responsible for a large percentage of hereditary PCC/PGL and that SDHB mutations are strongly correlated with extra-adrenal tumor location, metastasis, and poor prognosis. Further, gastrointestinal stromal tumors and renal tumors are now associated with SDHx mutations. A PCC or PGL caused by any of the hereditary susceptibility genes can present as a solitary, apparently sporadic, tumor, and substantial numbers of patients presenting with apparently sporadic tumors harbor occult germline mutations of susceptibility genes. Current roles of pathologists are differential diagnosis of primary tumors and metastases, identification of clues to occult hereditary disease, and triaging of patients for optimal genetic testing by immunohistochemical staining of tumor tissue for the loss of SDHB and SDHA protein. Diagnostic pitfalls are posed by morphological variants of PCC/PGL, unusual anatomic sites of occurrence, and coexisting neuroendocrine tumors of other types in some hereditary syndromes. These pitfalls can be avoided by judicious use of appropriate immunohistochemical stains. Aside from loss of staining for SDHB, criteria for predicting risk of metastasis are still controversial, and "malignancy" is diagnosed only after metastases have occurred. All PCCs/PGLs are considered to pose some risk of metastasis, and long-term follow-up is advised.

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.

Urinary retention due to benign tumor of the bladder neck in a woman; a rare case of papillary cystitis

BACKGROUND

Urinary retention (UR) is not common in women. There are numerous causes now recognized in women, broadly categorized as infective, pharmacological, neurological, anatomical, myopathic and functional. As opposed to the male, obstructive UR is unusual in women.

METHODS

A 56-year-old woman presented with urinary retention. She reported difficulty in urination for more than 15 days. She had no history of urinary tract infection, bladder surgery and catheterization. Her physical examination revealed a soft tissue mass obstructing the external orifice of the urethra. After its partial removal the patient regained her ability to urinate.

RESULTS

The patient underwent urological investigation. Ultrasound examination of the urinary system was normal. Cystoscopic examination revealed a papillary lesion with broad base floating along the bladder neck. The patient underwent transurethral resection of the bladder tumor.

DISCUSSION

Pathological examination diagnosed papillary cystitis. She was scheduled for a regular follow-up with urine cytology, ultrasound and cystoscopy. One year after diagnosis the patient remains free of symptoms and no recurrence was observed.

CONCLUSIONS

Papillary and polypoid cystitis are benign lesions, however under certain circumstances they should be considered in the differential diagnosis of transitional cell carcinoma of the bladder. Lack of the prominent inflammation and edema that characterizes both papillary and polypoid cystitis, and absence of a history of recent bladder catheterization and presence of vesical fistula may facilitate the decision to biopsy the lesion. To our knowledge, this is the first case of papillary cystitis presenting with urinary retention in a woman to be reported in the literature.

The spectrum of morphology in non-neoplastic prostate including cancer mimics

The spectrum of morphology in non-neoplastic prostate includes lesions of prostatic epithelial origin, the most common being atrophy, including partial atrophy, adenosis (atypical adenomatous hyperplasia), basal cell hyperplasia and crowded benign glands, as well as those of non-prostatic origin, such as seminal vesicle epithelium. These lesions often mimic lower-grade prostatic adenocarcinoma whereas others, such as granulomatous prostatitis, for example, are in the differential diagnosis of adenocarcinoma, Gleason grades 4 or 5. Diagnostic awareness of the salient histomorphological and relevant immunohistochemical features of these prostatic pseudoneoplasms is critical to avoid rendering false positive diagnoses of malignancy.

Seminal vesicle involvement by urothelial carcinoma in situ of the bladder with mucosal spread pattern: a case report

Mucosal spreading of urothelial tumors to the seminal vesicles is very rare. We experienced a case of mucosal involvement of the seminal vesicles by a bladder tumor in a 72-year-old man. The patient had a history of transurethral resection for invasive urothelial carcinoma of the bladder 8 years previously. Radical cystoprostatectomy was performed owing to recurrent and multiple urothelial carcinoma in situ. Microscopically, the urothelial carcinoma in situ was throughout the mucosa of the urinary bladder, both ureters, the prostate, and the left seminal vesicle. To date, the implication of mucosal involvement of the seminal vesicles by urothelial carcinoma is unclear. However, careful microscopic examination is needed to avoid an erroneous diagnosis.

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.

Polyps and masses of the pediatric urinary bladder: a 21-year pathology review

Although not uncommon in adults, bladder tumors are rare in children. In addition, the histologic types of tumors seen in the pediatric population differ from those seen in adults. Although rhabdomyosarcoma is the most common pediatric bladder tumor, many other benign, malignant, and reactive lesions can be encountered. All may present clinically as a mass or polyp in the bladder. This study was designed to describe the pathology and patient demographics of pediatric bladder masses, because there are few studies describing these entities. Retrospectively reviewing our experience over a 21-year period, we identified 98 specimens from 65 patients with polyps or masses in the urinary bladder. As expected, the most frequent diagnosis was rhabdomyosarcoma. This was followed by fibroepithelial polyp and a variety of additional nonurothelial tumors. Only 7 urothelial tumors were identified, including 1 low-grade papillary urothelial carcinoma. Inflammatory lesions, such as cystitis cystica and nephrogenic adenoma, were invariably associated with an irritating factor when a history was provided. Our findings emphasize that diagnoses made in the pediatric urinary bladder are distinct from those in adults, although a wide variety of lesions may still be seen.

Blue Nevus of the Prostate

Blue nevus is one of the melanotic lesions that can incidentally arise in the prostate gland. A literature review identified 28 previously reported cases, and although rare, the blue nevus appeared to be the commonest melanocytic lesion arising in the prostate. The differential diagnosis includes melanosis and malignant melanoma, as well as nonmelanotic lesions due to deposition of lipofuscin, hemosiderin and, rarely, homogentisic acid. The distinction among these lesions can typically be made based on morphologic grounds but may also be aided by histochemical and immunohistochemical stains such as stains for iron, S100 protein, HMB-45, and CD68 as needed. Blue nevus of the prostate is a benign lesion with no malignant potential to date, so no further treatment is warranted.

The transcription factor MIST1 is a novel human gastric chief cell marker whose expression is lost in metaplasia, dysplasia, and carcinoma

The lack of reliable molecular markers for normal differentiated epithelial cells limits understanding of human gastric carcinogenesis. Recognized precursor lesions for gastric adenocarcinoma are intestinal metaplasia and spasmolytic polypeptide expressing metaplasia (SPEM), defined here by ectopic CDX2 and TFF2 expression, respectively. In mice, expression of the bHLH transcription factor MIST1, normally restricted to mature chief cells, is down-regulated as chief cells undergo experimentally induced metaplasia. Here, we show MIST1 expression is also a specific marker of human chief cells. SPEM, with and without MIST1, is present in human lesions and, akin to murine data, likely represents transitional (TFF2(+)/MIST1(+) = "hybrid"-SPEM) and established (TFF2(+)/MIST1(-) = SPEM) stages. Co-visualization of MIST1 and CDX2 shows similar progressive loss of MIST1 with a transitional, CDX2(+)/MIST1(-) hybrid-intestinal metaplasia stage. Interinstitutional analysis and comparison of findings in tissue microarrays, resection specimens, and biopsies (n > 400 samples), comprising the entire spectrum of recognized stages of gastric carcinogenesis, confirm MIST1 expression is restricted to the chief cell compartment in normal oxyntic mucosa, rare in established metaplastic lesions, and lost in intraepithelial neoplasia/dysplasia and carcinoma of various types with the exception of rare chief cell carcinoma ( approximately 1%). Our findings implicate MIST1 as a reliable marker of mature, healthy chief cells, and we provide the first evidence that metaplasia in humans arises at least in part from the chief cell lineage.