Immunohistochemistry in the Differential Diagnosis Between Primary and Secondary Intestinal Adenocarcinoma of the Urinary Bladder

Urachal carcinoma: The journey so far and the road ahead

Urachal carcinoma, a rare cancer arising from urachus, accounts for about 1% of bladder cancer. The diagnosis at stage I shows about 63% 5-year survival whereas only 8% of the patients at stage IV shows a 5-year survival. Above 90% of urachal carcinomas are adenocarcinomas and most of the urachal carcinoma cases are invasive, showing a high resemblance to adenocarcinoma of various origins, making it hard for a conclusive diagnosis. Even though inconclusive, immunohistochemistry can play a significant role in identifying urachal carcinoma. Most cases show the biomarkers CK20 and CDX2, whereas CK7 and β-catenin are expressed at a lesser frequency. Due to the few cases available, there is a lack of evidence regarding specific markers differentiating urachal carcinoma from colorectal or primary bladder adenocarcinomas. In addition to immunohistochemistry, genomic characterization is emerging to play a role in the classification and treatment of the disease. Urachal carcinoma has been reported to have a molecular level similarity with colorectal malignancies regarding certain gene expressions. The TP53 mutations inactivating the tumor suppressor can probably be explored as a possible target in treating urachal carcinoma. Additionally, certain targets identified in gastric and breast cancer along with anti-HER2 treatment strategies can be explored. Immuno-oncology utilizes immune checkpoint inhibitors for the treatment of MSI-H tumors whereas a combination of tyrosine kinase inhibitors along with immune checkpoint inhibitors are being studied to treat MSI stable tumors. The article is an in-depth overview of urachal carcinoma addressing the current landscape with an emphasis on the future scenario.

Urachal carcinoma: a large retrospective multicentric study from the French Genito-Urinary Tumor Group

Introduction

Urachal cancer (UrC) is a rare, non-urothelial malignancy. Its natural history and management are poorly understood. Although localized to the bladder dome, the most common histological subtype of UrC is adenocarcinoma. UrC develops from an embryonic remnant, and is frequently diagnosed in advanced stage with poor prognosis. The treatment is not standardized, and based only on case reports and small series. This large retrospective multicentric study was conducted by the French Genito-Urinary Tumor Group to gain a better understanding of UrC.

Material and Methods

data has been collected retrospectively on 97 patients treated at 22 French Cancer Centers between 1996 and 2020.

Results

The median follow-up was 59 months (range 44-96). The median age at diagnosis was 53 years (range 20-86), 45% were females and 23% had tobacco exposure. For patients with localized disease (Mayo I-II, n=46) and with lymph-node invasion (Mayo III, n=13) median progression-free-survival (mPFS) was 31 months (95% CI: 20-67) and 7 months (95% CI: 6-not reached (NR)), and median overall survival (mOS) was 73 months (95% CI: 57-NR) and 22 months (95% CI: 21-NR) respectively. For 45 patients with Mayo I-III had secondary metastatic progression, and 20 patients were metastatic at diagnosis. Metastatic localization was peritoneal for 54% of patients. Most patients with localized tumor were treated with partial cystectomy, with mPFS of 20 months (95% CI: 14-49), and only 12 patients received adjuvant therapy. Metastatic patients (Mayo IV) had a mOS of 23 months (95% CI: 19-33) and 69% received a platin-fluorouracil combination treatment.

Conclusion

UrC is a rare tumor of the bladder where patients are younger with a higher number of females, and a lower tobacco exposure than in standard urothelial carcinoma. For localized tumor, partial cystectomy is recommended. The mOS and mPFS were low, notably for patients with lymph node invasion. For metastatic patients the prognosis is poor and standard therapy is not well-defined. Further clinical and biological knowledge are needed.

Urothelial Carcinoma: Divergent Differentiation and Morphologic Subtypes

Urothelial carcinoma (UC) is known to encompass a wide spectrum of morphologic features and molecular alterations. Approximately 15% to 25% of invasive UC exhibits histomorphologic features in the form of "divergent differentiation" along other epithelial lineages, or different "subtypes" of urothelial or sarcomatoid differentiation. It is recommended that the percentage of divergent differentiation and or subtype(s) be reported whenever possible. Recent advances in molecular biology have led to a better understanding of the molecular underpinning of these morphologic variations. In this review, we highlight histologic characteristics of the divergent differentiation and subtypes recognized by the latest version of WHO classification, with updates on their molecular and clinical features.

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.

Biomarkers in Urachal Cancer and Adenocarcinomas in the Bladder: A Comprehensive Review Supplemented by Own Data

Urachal cancer (UrC) is a rare but aggressive cancer. Due to overlapping histomorphology, discrimination of urachal from primary bladder adenocarcinomas (PBAC) and adenocarcinomas secondarily involving the bladder (particularly colorectal adenocarcinomas, CRC) can be challenging. Therefore, we aimed to give an overview of helpful (immunohistochemical) biomarkers and clinicopathological factors in addition to survival analyses and included institutional data from 12 urachal adenocarcinomas. A PubMed search yielded 319 suitable studies since 1930 in the English literature with 1984 cases of UrC including 1834 adenocarcinomas (92%) and 150 nonadenocarcinomas (8%). UrC was more common in men (63%), showed a median age at diagnosis of 50.8 years and a median tumor size of 6.0 cm. No associations were noted for overall survival and progression-free survival (PFS) and clinicopathological factors beside a favorable PFS in male patients (p = 0.047). The immunohistochemical markers found to be potentially helpful in the differential diagnostic situation are AMACR and CK34βE12 (UrC versus CRC and PBAC), CK7, β-Catenin and CD15 (UrC and PBAC versus CRC), and CEA and GATA3 (UrC and CRC versus PBAC). Serum markers like CEA, CA19-9 and CA125 might additionally be useful in the follow-up and monitoring of UrC.

Practical Immunohistochemistry in Neoplastic Pathology of the Gastrointestinal Tract, Liver, Biliary Tract, and Pancreas

CONTEXT

- Immunomarkers with diagnostic, therapeutic, or prognostic values have been increasingly used to maximize the benefits of clinical management of patients with neoplastic diseases of the gastrointestinal tract, liver, biliary tract, and pancreas.

OBJECTIVES

- To review the characteristics of immunomarkers that are commonly used in surgical pathology practice for neoplasms of the gastrointestinal tract, liver, biliary tract, and pancreas, and to summarize the clinical usefulness of immunomarkers that have been discovered in recent years in these fields.

DATA SOURCES

- Data sources include literature review, authors' research data, and personal practice experience.

CONCLUSIONS

- Immunohistochemistry is an indispensable tool for the accurate diagnosis of neoplastic diseases of the gastrointestinal tract, liver, biliary tract, and pancreas. Useful immunomarkers are available to help distinguish malignant neoplasms from benign conditions, determine organ origins, and subclassify neoplasms that are morphologically and biologically heterogeneous. Specific immunomarkers are also available to help guide patient treatment and assess disease aggressiveness, which are keys to the success of personalized medicine. Pathologists will continue to play a critical role in the discovery, validation, and application of new biomarkers, which will ultimately improve patient care.

Primary adenocarcinoma of the renal pelvis, ureter and the urinary bladder: A case report and review of the literature

Primary adenocarcinoma is a rare type of urological neoplasm. The present study reports the case of a 55-year-old man with multifocal adenocarcinoma of the renal pelvis, ureter and urinary bladder that occurred in association with a large cystic calculus and perinephric abscess. The patient had suffered from gross hematuria for 2 years and right flank pain for 2 months. Following a series of investigations, a large cystic calculus with multiple tumors in the renal pelvis and ureter was identified. Multifocal tumors and a large calculus were located in the bladder using a cystoscope. The pathological report of 3 individual biopsies revealed a moderately differentiated tubular adenocarcinoma. Right nephrectomy, ureterectomy, radical cystectomy and left ureterocutaneostomy were performed. The pathological investigation revealed a moderately differentiated adenocarcinoma of the renal pelvis, ureter and urinary bladder. No additional treatment was administered and the patient remains alive at follow-up without disease recurrence or metastasis. Although uncommon, the development of a tumor is possible in patients that possess long-standing urolithiasis, particularly when accompanied by hydronephrosis or infection.

Distinguishing primary adenocarcinoma of the urinary bladder from secondary involvement by colorectal adenocarcinoma: extended immunohistochemical profiles emphasizing novel markers

Glandular neoplasms involving the urinary bladder carry a challenging differential diagnosis including primary and secondary processes. We investigated the potential diagnostic utility of cadherin-17 and GATA3 in 25 primary adenocarcinomas of the urinary bladder, as compared with other commonly used markers including β-catenin and p63. Urothelial carcinoma with glandular differentiation (11), colorectal adenocarcinoma secondarily involving the bladder (25), and primary colorectal adenocarcinoma (22) were also analyzed and the results were compared using a Fisher exact test. Cadherin-17 was expressed in 23/25 primary bladder adenocarcinomas (92%), 23/25 colorectal adenocarcinomas involving the bladder (92%), 21/22 primary colorectal adenocarcinomas (95%) and entirely negative (0/11) in both components of urothelial carcinoma with glandular differentiation (P<0.001). In urothelial carcinoma with glandular differentiation, positive nuclear staining for GATA3 was evident in the urothelial component for 18% (2/11) and the glandular component for 9% (1/11) with additional tumors showing only cytoplasmic staining. Nuclear reactivity for GATA3 was not present in primary bladder adenocarcinoma and primary/secondary colorectal adenocarcinoma (P<0.05). Positive nuclear and cytoplasmic immunostaining for β-catenin was evident in 21/22 primary colorectal adenocarcinomas (95%) and 23/25 cases of secondary involvement by colorectal adenocarcinoma (92%). In contrast, positive membranous and cytoplasmic staining for β-catenin was observed in 23/25 primary bladder adenocarcinomas (92%) and 11/11 urothelial carcinomas with glandular differentiation (100%, P<0.001). p63 was expressed only in the urothelial component of urothelial carcinoma with glandular differentiation and not in the glandular component (P<0.001). In summary, cadherin-17 is a relatively specific and sensitive marker for primary adenocarcinoma of the urinary bladder, distinguishing it from urothelial carcinoma with glandular differentiation. However, it does not distinguish primary bladder adenocarcinoma from secondary involvement by colorectal adenocarcinoma. The pattern of reactivity for β-catenin remains the most useful marker for distinguishing these two tumors.

Primary bladder adenocarcinoma versus metastatic colorectal adenocarcinoma: a persisting diagnostic challenge

Aim

This study attempted to distinguish primary bladder adenocarcinoma (PBA) from metastatic colonic adenocarcinomas (MCA), which is a difficult diagnostic and clinical problem.

Methods

Twenty-four cases of bladder adenocarcinomas (12 primary & 12 metastatic colorectal) were included in the study with urothelial carcinoma (UC) and colonic adenocarcinoma (CA) as controls. A panel of immunohistochemical (IHC) stains along with fluorescence in-situ hybridization (FISH), using the UroVysion probe set, was performed.

Results

The majority of the PBAs presented with advanced disease. Enteric histologic subtype was the most common morphological variant. Strong nuclear with cytoplasmic-membranous staining of β-catenin was seen in 75% of MCA and only 16.7% PBA (<10% staining cells). Although abnormal nuclear staining with E-cadherin was seen in both PBA and MCA, it was more frequent in former. CK-7, CK-20, villin and CDX-2 stains were not helpful in distinguishing the two entities. FISH did not reveal any unique differences in chromosomal abnormality between the two groups.

Conclusion

Although there was a statistically significant difference in β-catenin and E-cadherin staining between two groups, we did not find any IHC or FISH marker that was specific for PBA. Distinction between PBA and MCA remains a diagnostic problem and clinical correlation is vital before rendering a diagnosis.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1393156268152357

Immunohistochemical features of the gastrointestinal tract tumors

Gastrointestinal tract tumors include a wide variety of vastly different tumors and on a whole are one of the most common malignancies in western countries. These tumors often present at late stages as distant metastases which are then biopsied and may be difficult to differentiate without the aid of immunohistochemical stains. With the exception of pancreatic and biliary tumors where there are no distinct immunohistochemical patterns, most gastrointestinal tumors can be differentiated by their unique immunohistochemical profile. As the size of biopsies decrease, the role of immunohistochemical stains will become even more important in determining the origin and differentiation of gastrointestinal tract tumors.

Immunohistochemistry of colorectal carcinoma: current practice and evolving applications

The relatively high incidence of adenocarcinoma of the colon and rectum (colorectal carcinoma) in the general population makes its pathologic diagnosis one of the more frequent exercises in anatomical pathology. Although typically mundane in the primary setting, the correct identification of metastatic colorectal carcinoma or exclusion of metastatic disease from carcinoma arising in other anatomical foci can be problematic. The advent of targeted therapies and refinement of more traditional cytotoxic chemotherapeutic regimens mandates not only a more confident appraisal of site of origin but also assessment of those tumor-specific features that may alter therapeutic decisions. Despite the exponential increase in our understanding of the molecular pathogenesis of colorectal carcinoma, immunohistochemistry remains the foundation for resolution of these problematic cases and the number of antibodies available to the practicing pathologist continues to expand at a steady rate. In some cases, immunohistochemistry may also provide valuable prognostic information, either independently or as a surrogate marker for a specific route of carcinogenesis such as microsatellite instability. This review will focus on the use of new and more established immunohistochemistry markers in the diagnosis of colorectal carcinoma, with an emphasis on aberrant staining patterns of the various colorectal carcinoma subtypes as well as the utility of these markers in specific differential diagnostic settings.

Signet-ring-cell carcinoma of stomach metastatic to the bladder: a case report with cytological and histological correlation and literature review

BACKGROUND

Bladder involvement by a secondary tumor is fairly rare and an uncommon source of bladder metastasis is the stomach.

CASE REPORT

The authors report a case of a 38-year-old man with a bladder metastasis from a gastric signet-ring-cell (SRC) adenocarcinoma who presented with ematuria. The clinical history and the presence of SRCs in the voided urinary cytology and histologically in the suburothelial connective, with an overlying intact urothelium suggested a diagnosis of bladder metastasis from gastric carcinoma.

CONCLUSION

Bladder involvement by a secondary tumor is very rare, and a SRC carcinoma metastatic to the bladder, albeit extremely rare, should be considered in the differential diagnosis.

Differentiating rectal carcinoma by an immunohistological analysis of carcinomas of pelvic organs based on the NCBI Literature Survey and the Human Protein Atlas database

The treatments and prognoses of pelvic organ carcinomas differ, depending on whether the primary tumor originated in the rectum, urinary bladder, prostate, ovary, or uterus; therefore, it is essential to diagnose pathologically the primary origin and stages of these tumors. To establish the panels of immunohistochemical markers for differential diagnosis, we reviewed 91 of the NCBI articles on these topics and found that the results correlated closely with those of the public protein database, the Human Protein Atlas. The results revealed the panels of immunohistochemical markers for the differential diagnosis of rectal adenocarcinoma, in which [+] designates positivity in rectal adenocarcinoma and [-] designates negativity in rectal adenocarcinoma: from bladder adenocarcinoma, CDX2[+], VIL1[+], KRT7[-], THBD[-] and UPK3A[-]; from prostate adenocarcinoma, CDX2[+], VIL1[+], CEACAM5[+], KLK3(PSA)[-], ACPP(PAP)[-] and SLC45A3(prostein)[-]; and from ovarian mucinous adenocarcinoma, CEACAM5[+], VIL1[+], CDX2[+], KRT7[-] and MUC5AC[-]. The panels of markers distinguishing ovarian serous adenocarcinoma, cervical carcinoma, and endometrial adenocarcinoma were also represented. Such a comprehensive review on the differential diagnosis of carcinomas of pelvic organs has not been reported before. Thus, much information has been accumulated in public databases to provide an invaluable resource for clinicians and researchers.

Adenocarcinoma of the Urinary Bladder

Primary adenocarcinoma of urinary bladder is an uncommon neoplasm and is a source of diagnostic confusion with adenocarcinomas arising in adjacent organs, especially colon. These tumors show varied histologic picture and degree of differentiation. Clinical association with bladder exstrophy and schistosomiasis has been well documented. Primary bladder adenocarcinomas have overlapping histologic and immunohistochemical features with adenocarcinomas arising from other primary sites and the suggested immunohistochemical panel includes cytokeratins 7 and 20, 34βE12, thrombomodulin, CDX2, and β-catenin. Clinical, imaging, histologic, and immunohistochemical correlation should be done while rendering this diagnosis, as prognosis and therapeutic options for primary versus metastatic adenocarcinoma vary widely.

Metastatic tumors to the urinary bladder: clinicopathologic study of 11 cases

Secondary neoplasms of the urinary bladder are uncommon, with metastatic tumors being an even rarer event. The authors studied the clinicopathology of 11 cases of metastatic tumors to bladder, which were collected from their archives between 1995 and 2010. The most common metastases in this series were breast. Some unusual metastases, including several not being previously reported, were also presented, namely, ileal carcinoid tumor, ileal gastrointestinal stromal tumor, ovarian squamous carcinoma, pancreatic gastrinoma, and renal collecting duct carcinoma. Vast majority of these patients (10/11, 91%) were female. Ninety percent of the patients presented with hematuria and/or obstructive urinary symptom as well as bladder lesions in the area of trigone, posterior wall, and/or bladder neck. Seven of the 11 patients had a known history of other metastases besides the bladder. Most of the patients (4/7, 57%) died within 1 year after diagnosis of bladder metastasis. Metastasis must be distinguished from a primary bladder neoplasm. Morphology and clinical correlation supplemented with immunohistochemical study is critical for the correct diagnosis.

Mucin-producing urothelial-type adenocarcinoma of the prostate as a mimicker of colonic adenocarcinoma: a case report and review of the literature

A 59-year-old man presented with persistent urinary obstructive symptoms, gross hematuria, and mucusuria. Subsequently, a prostate-specific antigen (PSA)-negative mucin-producing urothelial type adenocarcinoma of prostate was found. The serum PSA level was within the normal limit. Colonoscopy, positron emission tomography, and other tumor surveys showed this to be the only prostate lesion. Microscopically, there was an adenocarcinoma with copious mucin production, with the formation of mucin pools. The neoplastic glands were variously arranged in cribriform, glandular, and villous adenoma-like patterns. This is a very rare tumor, of which there are only 20 cases reported in the literature in the English language. It is critical to distinguish it from mucinous acinar adenocarcinoma of the prostate and from metastatic adenocarcinoma of either the bladder or colon. This is mainly because mucin-producing urothelial type adenocarcinoma of the prostate has a different clinical behavior, and hence, the treatment plan is different from that for conventional prostatic adenocarcinoma. Specifically, it has a more aggressive clinical course and is unresponsive to hormone therapy.

Sustained response of adenocarcinoma of the urinary bladder to FOLFOX plus bevacizumab

BACKGROUND

A 44-year-old patient presented with intermittent macroscopic hematuria on a background of chronic left-sided hydronephrosis and intestinal metaplasia of the bladder. Cystoscopic examination revealed a mass at the dome of the urinary bladder, which was resected. Histopathologic analysis of the specimen confirmed the presence of muscle-invasive adenocarcinoma. Radical cystectomy with curative intent was planned, but review of systems and subsequent CT demonstrated pleural effusion with positive cytology, confirming metastatic disease. Owing to the histologic similarity between this patient's tumor and colorectal cancer, palliative FOLFOX6 (folinic acid, 5-fluorouracil and oxaliplatin) chemotherapy plus bevacizumab was administered. After 3 months of treatment the patient showed a good response, which was sustained for more than 10 months after diagnosis. However, his disease subsequently relapsed, and the patient died shortly thereafter.

INVESTIGATION

Physical examination, cystoscopy, transurethral resection of bladder tissue, CT, histopathologic, cytopathologic and immunohistochemical analysis.

DIAGNOSIS

Metastatic adenocarcinoma of the urinary bladder.

MANAGEMENT

12 cycles of infused and bolus 5-fluorouracil, folinic acid and oxaliplatin (FOLFOX6) plus bevacizumab.

Metastatic Small Intestinal Cancer of the Urinary Bladder

We report an extremely rare case of small intestinal cancer metastasized to the urinary bladder, presenting a urologic symptom. A 41-year-old man first presented with nausea, vomiting and abdominal pain. Based on the clinical diagnosis of jejunal cancer, he underwent a partial resection of the jejunum with lymph node dissection. The pathological diagnosis was moderately differentiated adenocarcinoma of the jejunum, pT4N0. Seventeen months after surgery, he presented with a gross hematuria. Computed tomographic scan showed wall thickening of the posterior wall of the urinary bladder. No tumor was found in other organs or lymph nodes. Based on histological and immunohistochemical analysis, the diagnosis of urinary bladder metastasis from jejunal adenocarcinoma was made. This is the first report of urinary bladder metastasis from small intestinal cancer. Although very rare, the possibility of metastatic small intestinal cancer should be considered in differential diagnosis in patients with adenocarcinoma involving the urinary bladder.

[Primary adenocarcinoma of a ureteral remnant stump after nephrectomy]

AIM

Adenocarcinomas of the upper urinary tract are very rare malignancies often related to primary genitourinary and extraurinary tumours. Primary adenocarcinomas are even rarer. There are no clinical guidelines for the management of primary ureteral adenocarcinoma. Our objective is to propose a management algoritm of this sort of tumours.

METHODS

We report a case of adenocarcinoma affecting a ureteral stump in a patient who previously underwent a nephrectomy. A review of literature is performed.

RESULTS

After the ureterectomy the pathologist diagnosed a ureteral adenocarcinoma. We performed an extension study in order to discard an extraurinary origin.

CONCLUSIONS

Adenocarcinoma of the ureteral stump is a very rare malignancy. About the clinic and pathologic characterization, there is no an established reference due to the short number of previous reports. Clinical presentation may include previous nephrectomy, flank pain, dysuria, urgency and/or gross hematuria. It seem necessary the complete resection of the urinary tract when a nephrectomy is performed. Adjuvant chemotherapy can be employed with uncertain results.

Secondary neoplasms of the urinary system and male genital organs

BACKGROUND AND AIMS

In this review we discuss those secondary tumours involving the urinary system and male genital organs that can pose differential diagnostic difficulties with primary lesions, and highlight morphological and ancillary features that could be helpful in reaching a proper assignment of primary origin.

MATERIALS AND METHODS

Based on MEDLINE database searches all reports of secondary tumours involving the urinary system (kidney and bladder) and male genital organs (prostate, testis and penis) were examined.

RESULTS AND DISCUSSION

Involvement by a secondary tumour occurs either as a metastasis or by direct extension. Among non-genitourinary primary sites, colorectal, pulmonary, skin (melanoma) and breast are the most common contributors. Secondary spread from a genitourinary site primary tumour to another genitourinary organ occurs most frequently between the prostate and urinary bladder, given the intimate topographic proximity of the two. The prognosis is very poor, as the secondary tumour usually occurs in patients with carcinoma in the late stages. Few secondary tumours have distinctive histological and immunohistochemical features, making it difficult to make the appropriate diagnosis. Hence, knowledge of the history and clinical setting are particularly important in these cases.

CONCLUSION

The urinary system and male genital organs are not common sites for secondary tumours. They often go either undiagnosed or misdiagnosed in the clinical follow-up of patients with cancer. Accurate diagnosis is essential because of differing therapeutic approaches compared with a primary neoplasm.

A case of relapsing secondary bladder adenocarcinoma after right colonic cancer

BACKGROUND

A 71-year-old woman was referred to a surgical oncology clinic after CT raised suspicion for a bladder neoplasm. She had previously undergone right hemicolectomy and received adjuvant chemotherapy for pT3N1MX cancer of the cecum. A retroperitoneal recurrence had been deemed unsuitable for surgical resection, and had instead been treated with chemoradiation therapy. Follow-up CT raised suspicion for a possible bladder neoplasm.

INVESTIGATIONS

CT, physical examination, urinalysis, cystoscopy with biopsy, pathological analysis and immunohistochemical analysis.

DIAGNOSIS

Adenocarcinoma of the cecum metastatic to the bladder.

MANAGEMENT

The patient underwent open bladder resection with total excision of the neoplasm and was administered adjuvant chemotherapy consisting of irinotecan and cetuximab. Subsequent recurrences at the same site were treated with transurethral resection, while chemotherapy was still in progress. At 7 months' follow-up, the patient remained alive, with no evidence of further recurrence.

Distinguishing benign dissecting mucin (stromal mucin pools) from invasive mucinous carcinoma

Mucin dissecting stroma suggests the presence of an invasive mucinous (colloid) carcinoma. However, in virtually every organ in which invasive mucinous carcinoma exists, there exist benign mimickers associated with dissecting mucin. This article reviews diagnostic criteria for the differential diagnosis of mucinous lesions of the breast, pancreas, biliary tract, colon, appendix, and bladder, emphasizing practical points, which we find helpful in daily diagnostic surgical pathology practice.