Nephrogenic Adenoma of the Bladder

Nephrogenic adenoma of the renal pelvis: A rare case report and review of the literature

RATIONALE

Nephrogenic adenoma (NA) is a rare benign lesion of the urinary tract, which rarely occurs in the renal pelvis. Only 19 cases have been reported in the literature. However, there is no detailed report on the clinicopathological features of NA of the renal pelvis.

PATIENT CONCERNS

This case report describes a 46-year-old male patient who was admitted to the hospital for one month because of painless gross hematuria with blood clots. He had a history of hyperuricemia and a family history of gastric cancer.

DIAGNOSES

NA of the renal pelvis was diagnosed pathologically and immunohistochemical.

INTERVENTIONS

The patient underwent laparoscopic nephroureterectomy.

OUTCOMES

The patient recovered well after the operation with no discomfort. In addition, we followed up with the patient regularly post-discharge (approximately 20 months). There were no obvious abnormalities in the results of routine urine culture, computed tomography scan of the abdomen, and cystoscopy during the follow-up period, and the symptoms disappeared completely and did not recur.

LESSONS

NA of the renal pelvis is extremely rare in the clinic, which can be easily misdiagnosed and overtreated. However, for pathological diagnosis of this disease, specific immunohistochemical staining for preoperative biopsy was reported to be significant, which should be considered by the urologists and pathologists.

Urothelial Cancer Stem Cell Heterogeneity

Urothelial carcinoma is a tumor type featuring pronounced intertumoral heterogeneity and a high mutational and epigenetic load. The two major histopathological urothelial carcinoma types - the non-muscle-invasive and muscle-invasive urothelial carcinoma - markedly differ in terms of their respective typical mutational profiles and also by their probable cells of origin, that is, a urothelial basal cell for muscle-invasive carcinomas and a urothelial intermediate cell for at least a large part of non-muscle-invasive carcinomas. Both non-muscle-invasive and muscle-invasive urothelial carcinomas can be further classified into discrete intrinsic subtypes based on their typical transcriptomic profiles. Urothelial carcinogenesis shows a number of parallels to a urothelial regenerative response. Both of these processes seem to be dominated by specific stem cell populations. In the last years, the nature and location of urothelial stem cell(s) have been subject to many controversies, which now seem to be settled down, favoring the existence of a largely single urothelial stem cell type located among basal cells. Basal cell markers have also been amply used to identify urothelial carcinoma stem cells, especially in muscle-invasive disease, but they proved useful even in some non-muscle-invasive tumors. Analyses on molecular nature of urothelial carcinoma stem cells performed till now point to their great heterogeneity, both during the tumor development and upon intertumoral comparison, sexual dimorphism providing a special example of the latter. Moreover, urothelial cancer stem cells are endowed with intrinsic plasticity, whereby they can modulate their stemness in relation to other tumor-related traits, especially motility and invasiveness. Such transitional modulations suggest underlying epigenetic mechanisms and, even within this context, inter- and intratumoral heterogeneity becomes apparent. Multiple molecular aspects of urothelial cancer stem cell biology markedly influence therapeutic response, implying their knowledge as a prerequisite to improved therapies of this disease. At the same time, the notion of urothelial cancer stem cell heterogeneity implies that this therapeutic benefit would be most probably and most efficiently achieved within the context of individualized antitumor therapy.

Nephrogenic Adenoma: Clinical Features, Management, and Diagnostic Pitfalls

OBJECTIVE

To review the diagnosis and management of nephrogenic adenoma (NA), an uncommon benign lesion found in the urinary tract. This lesion arises from a proliferation of implanted renal tubular cells. Although more common in adults, it can occur in all ages. NAs can recur and cause significant morbidity in patients. NAs are also a potential diagnostic pitfall as they can clinically and histologically mimic malignancy in the urinary tract.

MATERIALS AND METHODS

We performed an Institutional Board Review approved search of our surgical pathology database from 2005 to 2015 for cases of NA. A retrospective chart review was performed with a focus on the clinical, pathologic, and radiographic findings in these patients.

RESULTS

We identified 32 cases of NA in 31 patients. Lesions were most common in Caucasian males (male-to-female ratio of 2:1) with an average age at diagnosis of 55 years (range 25-77). Bladder was the most common site of occurrence (81.2%), followed by ureter (9.4%), urethra (6.3%), and intrarenal collecting system (3.1%). Most patients (72%) were symptomatic and presented with hematuria (41%), lower urinary tract symptoms (28%), pelvic or flank pain (6%), hydronephrosis (19%), or urinary incontinence (13%). NA was asymptomatic and identified incidentally in 9 (28%) patients. One patient (3%) had a renal transplant and 8 (26%) patients had diabetes mellitus. Twenty-six (84%) patients were managed with endoscopic resection of their tumors.

CONCLUSION

NAs are benign lesions that may cause significant morbidity and mimic malignant tumors. There should be increased suspicion in patients with predisposing factors.

Rare cause of macroscopic hematuria in a pediatric patient: nephrogenic adenoma of the bladder

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.

Nephrogenic adenoma: an immunohistochemical analysis using biotin-free methods

Nephrogenic adenoma (NA) has been considered as a metaplastic process of the urothelium. It has been suggested that this lesion is of renal tubular cell origin or differentiation. Immunohistochemical studies of NA emphasize its staining with α-methylacyl-coenzyme A racemase (AMACR), and prostatic adenocarcinoma may be a possible differential diagnosis. This reactivity was recently discussed as an artifact due to endogenous biotin. Kidney-specific cadherin (Ksp-cad) is a marker of distal nephron. CD10 and KIT are also expressed in the kidney. We studied the immunohistochemical expression of AMACR, p63, Ksp-cad, CD10, and KIT in 9 cases of NA (forming a total of 12 lesions). Practically all of the lesions stained for AMACR with 2 different antibodies and 2 high-sensitivity (multimer or polymer based) biotin-free methods (83% and 100%). The staining was similar for both methods in 9 of these 12 lesions. All of the NAs were negative for p63 and KIT, except 1 case, with focal reactivity for KIT. CD10 was expressed very focally in 4 of the 12 lesions (33%). We observed weak staining for Ksp-cad in 6 lesions (50%) and 3 (25%) showed a moderate positivity in 15% to 50% of the cells. In conclusion, positivity of NA for AMACR is not an artifact, as we confirmed using 2 different methods. Besides, p63, a basal cell marker, is usually negative. Immunoreactivity for Ksp-cad seems to support the differentiation of NA to distal nephron cells, at least in some of the cases. Other markers expressed by the nephron, such as CD10 and KIT, are usually negative in NA.