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Nephrogenic adenoma (NA) is an epithelial lesion that usually occurs in the mucosa of the urinary tract. Rare cases of deep infiltrative or perinephric lesions have also been reported. Recently, NA with characteristic fibromyxoid stroma (fibromyxoid NA) has been proposed as a distinct variant. Although shedding of distal renal tubular cells due to urinary tract rupture has been postulated as the cause of NA in general, the mechanism underlying extraurinary presentation of NA and fibromyxoid stromal change in fibromyxoid NA remains unknown. In this study, we performed mass spectrometry (MS) analysis in a case of perinephric fibromyxoid NA of an 82‐year‐old man who underwent right nephroureterectomy for distal ureteral cancer. The patient had no prior history of urinary tract injury or radiation. Periodic acid‐Schiff staining‐positive eosinophilic structureless deposits in the stroma of fibromyxoid NA were microdissected and subjected to liquid chromatography/MS. The analysis revealed the presence of a substantial amount of uromodulin (Tamm−Horsfall protein). The presence of urinary content in the stroma of perinephric fibromyxoid NA suggests that urinary tract rupture and engraftment of renal tubular epithelial cells directly cause the lesion. [ABSTRACT FROM AUTHOR]

Conventional urothelial carcinoma accounts for most carcinomas of the urinary tract lining. However, neoplastic urothelium has the capacity to demonstrate enormous plasticity. A variety of unusual architectural patterns of urothelial carcinoma, such as the nested, microcystic and inverted variants, can be mistaken for reactive processes or benign tumours. Others such as the micropapillary, plasmacytoid and discohesive variants, can mimic metastatic tumour from other sites. The micropapillary variant in particular is more aggressive. In addition, urothelial carcinoma has a propensity to demonstrate divergent differentiation with glandular, squamous, small cell neuroendocrine, lymphoepithelioma-like, sarcomatoid or other elements. Pure squamous carcinoma or adenocarcinoma (the latter in particular) can be difficult to distinguish from contiguous or metastatic spread. Some variants have prognostic and potential therapeutic implications. Molecular genetic evidence has emerged recently supporting a close relationship between urothelial carcinoma and various divergent elements. Sarcomatoid carcinoma and its differential diagnosis with other spindle cell lesions of urinary tract will be covered in a separate review. [ABSTRACT FROM AUTHOR]

Objective To obtain information on the presenting symptoms, location, sex distribution, age, endoscopic appearance, histopathology, suitable treatment and recurrence of nephrogenic adenoma, a rare, benign lesion of the urinary tract mucosa. Patients and methods The records of 31 patients with nephrogenic adenoma diagnosed at the Sahlgrenska University Hospital between 1980 and 1996 were reviewed to determine the symptomatology, imaging investigations, endoscopic presentation, clinical outcome after resection and the frequency of recurrence. Results The lesions were found in the urinary bladder, bulbar urethra, urethral diverticula and the prostatic urethra. Eight patients presented with haematuria, 13 complained of urinary frequency and bladder pain and in 12 patients without subjective symptoms from the urinary tract, the lesion was found accidentally. Twenty-seven of the patients had a history of previous urothelial trauma, either by instrumentation or inflammation. Seventeen of the lesions were polypoid at endoscopy, the remainder being flat except for two cases, in which they were not noted because they were concealed in another lesion to be resected. Seven patients had one or more recurrences. All patients with symptoms responded well to transurethral resection. Conclusion Nephrogenic adenoma mimics tumour or chronic cystitis and it is rarely suspected on clinical grounds; instead, the diagnosis is almost always histological. This study supports the view that nephrogenic adenoma may represent a metaplastic response to trauma of the urothelium and that transurethral resection provides a good method of relieving the symptoms in symptomatic nephrogenic adenoma. [ABSTRACT FROM AUTHOR]

Pediatric nephrogenic adenoma ( NA) is an uncommon benign metaplastic lesion occurring in the urothelium. Herein we report a case of NA of the urinary bladder in a 14-year-old boy. The patient presented with macroscopic hematuria and had a history of ureteral surgery and long-term smoking. NA should be considered in the differential diagnosis of any urinary tract tumor in the pediatric population. [ABSTRACT FROM AUTHOR]

We describe a nephrogenic adenoma of the bladder in a 14-year-old girl with Turner's syndrome. The patient also had a past history of urological surgery for vesicoureteral reflux. In this case, the multifocal lesions were successfully treated by transurethral resection. [ABSTRACT FROM AUTHOR]

A 56-year-old male who had renal transplants at the age of 34 and 49 years, presented with painless gross hematuria six years after the second renal transplantation. An abdominal computed tomography scan revealed diffuse wall thickening of the distal ureter of the failed first allograft and a bulging lesion about 1.2 cm in size on the lower pole of the right native kidney. Both lesions were suspected for tumors, but they showed a ureteral nephrogenic adenoma and a renal hemorrhagic simple cyst. [ABSTRACT FROM AUTHOR]