Retroperitoneal laparoscopic partial nephrectomy for metanephric adenoma in a pediatric patient - The first case report from vietnam

Metanephric adenoma presents as a rare benign tumor in children with differentiated diagnoses: Wilms tumor or renal cell carcinoma. When confronted with small renal tumors, whether they fall into one of these three diagnostic categories, tumor resection surgery with laparoscopic partial nephrectomy is considered a viable and effective operative approach. Herein, we report the case of an 11-year-old female patient initially diagnosed with stage T1a renal cell carcinoma with postoperative pathology results confirming metanephric adenoma. Successfully treated with laparoscopic partial nephrectomy, the patient showed no signs of recurrence or metastasis during follow-up.

Metanephric adenoma diagnosed on biopsy in an infant: a case report

BACKGROUND

Metanephric adenoma is a rare benign renal tumor of the kidney, uncommonly observed in children. It is often misdiagnosed preoperatively as a malignant neoplasm, leading to an unnecessary nephrectomy. The challenge is to make the right diagnosis preoperatively and therefore manage it with conservative surgery. We report a case of a child with metanephric adenoma who underwent nephron-sparing surgery.

CASE PRESENTATION

A renal tumor was discovered fortuitously in an 18-month-old Caucasian girl with several congenital malformations. Investigations showed a 28 × 27 × 27 mm left renal mass centrally located, well defined, nonvascularized, with no calcifications and which compressed the adjacent renal tissue. Furthermore, there were no signs of metastasis. The decision of a multidisciplinary meeting was to perform a computed tomography (CT)-scan-guided biopsy. Histologic examination concluded it was a metanephric adenoma. We performed a left open partial nephrectomy via a flank retroperitoneal incision. The final histopathological examination confirmed the diagnosis. The postoperative course was uneventful.

CONCLUSION

Preoperative diagnosis of metanephric adenoma is challenging. Because of the high probability of unnecessary radical nephrectomy, preoperative biopsy can be safe and determining to guide a more conservative approach so nephron-sparing surgery can be performed.

Metanephric adenoma an unusual renal mass: A rare case

Metanephric adenoma is a rare benign mass that may be radiologically indistinguishable from renal cell carcinoma. The clinical presentation of this entity is similar to a malignant renal mass. Only 200 cases have been reported worldwide till now. Furthermore, there are no strongly predictive clinical and radiological criteria. It, therefore, poses a diagnostic challenge. Since post-operative therapy may vary significantly if the lesion turns out to be malignant, it is crucial to distinguish it from other malignant renal masses.

A giant metanephric adenoma in a young male

Metanephric adenoma is an uncommon renal tumor with almost exclusively benign behavior, which can clinically and radiologically imitate malignancy. The histological examination is therefore crucial in diagnosis. Herein, we report a case of an 18-year-old male with a huge left renal mass. Histopathology and immunohistochemistry of nephrectomy resection specimen confirmed it to be metanephric adenoma. We present our experience with this rare tumor entity and literature review with focusing on differential diagnosis.

Artificial intelligence-based multi-class histopathologic classification of kidney neoplasms

Artificial intelligence (AI)-based techniques are increasingly being explored as an emerging ancillary technique for improving accuracy and reproducibility of histopathological diagnosis. Renal cell carcinoma (RCC) is a malignancy responsible for 2% of cancer deaths worldwide. Given that RCC is a heterogenous disease, accurate histopathological classification is essential to separate aggressive subtypes from indolent ones and benign mimickers. There are early promising results using AI for RCC classification to distinguish between 2 and 3 subtypes of RCC. However, it is not clear how an AI-based model designed for multiple subtypes of RCCs, and benign mimickers would perform which is a scenario closer to the real practice of pathology. A computational model was created using 252 whole slide images (WSI) (clear cell RCC: 56, papillary RCC: 81, chromophobe RCC: 51, clear cell papillary RCC: 39, and, metanephric adenoma: 6). 298,071 patches were used to develop the AI-based image classifier. 298,071 patches (350 × 350-pixel) were used to develop the AI-based image classifier. The model was applied to a secondary dataset and demonstrated that 47/55 (85%) WSIs were correctly classified. This computational model showed excellent results except to distinguish clear cell RCC from clear cell papillary RCC. Further validation using multi-institutional large datasets and prospective studies are needed to determine the potential to translation to clinical practice.

Pediatric metanephric adenoma with Fanconi-Bickel syndrome: a case report and review of literature

Background

Metanephric adenoma (MA) is a rare benign renal tumor that resembles renal cell carcinoma and Wilms’ tumor in radiological as well as pathological appearance. It can present at any age or gender, and it is extremely rare in the pediatric age group with less than 50 reported cases. Fanconi–Bickel syndrome (FBS) is a rare autosomal recessive disorder of carbohydrate metabolism. Herein, we report a rare incidence of MA in a boy with a genetically confirmed FBS who underwent a nephron-sparing surgery.

Case presentation

A 21-month-old boy was referred to the pediatric urology clinic for further evaluation of an incidentally discovered left renal mass. His laboratory investigations showed normal renal function, hypophosphatemia, high blood glucose level, markedly elevated serum alkaline phosphatase, and low serum vitamin D. Blood picture showed signs of polycythemia and urinalysis showed glucosuria and aminoaciduria. Genetic testing was positive for Fanconi–Bickel syndrome. Radiological investigations were carried out with abdominal ultrasound and computerized tomography (CT) with intravenous contrast documented a sharply marginated peripheral hypoechoic hypovascular homogeneously enhancing mass at the upper pole of the left kidney measuring 2.0 × 1.8 × 2.0 cm. The child was admitted and started on supportive treatment until his medical condition was stabilized, then underwent elective open left partial nephrectomy via a left upper transverse abdominal transperitoneal incision. The excised renal mass was sent for histopathological assessment and was found to be a tumor composed of tightly packed tubules with no mitotic figures or necrosis and scanty cytoplasm consistent with MA. After good hydration and tumor resection, his polycythemia gradually improved. The patient was discharged home in a good condition with his proper replacement therapies. His follow-up abdominal ultrasound after 12 months showed no signs of recurrence.

Conclusions

Metanephric adenoma is extremely rare in the pediatric age group, especially in those who have a FBS. The only way to diagnose and treat this tumor is by surgical resection as most patients are asymptomatic. A nephron-sparing surgery is better for this age group in which the future renal function is considered.

Metastatic atypical renal tumour with metanephric characteristics treated with Sunitinib

Metanephric Adenoma (MA) is a rare and unclassifiable renal tumour with sparse reported clinical and morphological features. Generally MA's have a benign course without recurrence after nephrectomy, however a few cases received oncological treatment due to malignant progression.

We present a 42-year-old woman who years after an initial nephrectomy developed several processes and biopsy confirmed recurrence of MA. Sunitinib was given for only two weeks, as she developed side-effects and currently the patient undergoes control scans with only minimal growth of the processes.

This is the first case of MA treated with Tyrosin-Kinase-Inhibitor.

Metanephric adenoma with BRAF V600K mutation and a doubtful radiological imaging: pitfalls in the diagnostic process

Metanephric adenoma (MA) is an uncommon benign renal tumor whose histomorphological aspect resembles that of Wilms’ tumor and papillary renal cell carcinoma. From a diagnostic and therapeutic perspective, recognition of this entity is important as it has a more favorable clinical outcome compared with Wilms’ tumor and papillary renal cell carcinoma. MA should not be treated with nephrectomy if the tumor size is small, opting for a conservative treatment. However, the preoperative diagnosis of this disease is extremely challenging. The present study describes a case of this rare disease, showing an ambiguous radiological imaging and that only after a percutaneous biopsy, was defined as a MA and treated with partial nephrectomy. Moreover, the histological diagnosis of this case was partially complicated by the equivocal immunohistochemical analysis showing negativity for BRAF VE1 staining. Only the mutational analysis demonstrated the presence of the BRAF V600K mutation (for the first time described in a case of metanephric adenoma), highlighting the necessity of sequencing in case of MA with negativity for BRAF VE1 clone.

KANK1-NTRK3 fusions define a subset of BRAF mutation negative renal metanephric adenomas

Background

Metanephric adenoma (MA) is a rare benign renal neoplasm. On occasion, MA can be difficult to differentiate from renal malignancies such as papillary renal cell carcinoma in adults and Wilms̕ tumor in children. Despite recent advancements in tumor genomics, there is limited data available regarding the genetic alterations characteristic of MA. The purpose of this study is to determine the frequency of metanephric adenoma cases exhibiting cytogenetic aberration t (9;15)(p24;q24), and to investigate the association between t (9,15) and BRAF mutation in metanephric adenoma.

Methods

This study was conducted on 28 archival formalin fixed paraffin-embedded (FFPE) specimens from patients with pathologically confirmed MA. Tissue blocks were selected for BRAF sequencing and fluorescent in situ hybridization (FISH) analysis for chromosomal rearrangement between KANK1 on chromosome 9 (9p24.3) and NTRK3 on chromosome 15 (15q25.3), which was previously characterized and described in two MA cases.

Results

BRAF^V600E mutation was identified in 62% of our cases, 9 (38%) cases were BRAF^WT, and 4 cases were uninformative. Of the 20 tumors with FISH results, two (10%) were positive for KANK1-NTRK3 fusion. Both cases were BRAF^WT suggesting mutual exclusivity of BRAF^V600E and KANK1-NTRK3 fusion, the first such observation in the literature.

Conclusions

Our data shows that BRAF mutation in MA may not be as frequent as suggested in the literature and KANK-NTRK3 fusions may account for a subset of BRAF^WT cases in younger patients. FISH analysis for KANK1-NTRK3 fusion or conventional cytogenetic analysis may be warranted to establish the diagnosis of MA in morphologically and immunohistochemically ambiguous MA cases lacking BRAF mutations.

ALK-rearranged renal cell carcinoma with a novel PLEKHA7-ALK translocation and metanephric adenoma-like morphology

ALK-rearranged renal cell carcinoma is a provisional entity in the 2016 WHO Classification of Tumors of the Urinary System and Male Genital Organs. The reported fusion partners included VCL, TPM3, EML4, STRN, and HOOK1. Herein, we present a peculiar renal cell carcinoma morphologically resembling metanephric adenoma and harboring a novel PLEKHA7-ALK fusion. Microscopically, the tumor is composed of bland epithelial cells with scant to moderate amount of amphophilic cytoplasm, round and uniform nuclei, delicate chromatin, and inconspicuous nucleoli, arranged in tightly packed small acini and angulated tubules. Papillary formation, intraluminal glomeruloid tufts, microcysts, and solid nests were focally observed. Psammomatous calcifications were evident. The tumor cells were diffusely reactive for CK7, AMACR, PAX8, and ALK, while non-reactive for WT1, BRAF V600E, CD57, carbonic anhydrase IX, TFE3, and cathepsin K. Fluorescence in situ hybridization showed breaking apart of ALK. A novel PLEKHA7exon18-ALKexon20 fusion was detected using ArcherDX FusionPlex next-generation sequencing panel and was further confirmed with reverse-transcriptase PCR. Our case demonstrates that in contrast to prior cases showing high-grade tumor cells, ALK-rearranged renal cell carcinoma may also present as a low-grade renal tumor mimicking metanephric adenoma. Immunohistochemistry and molecular testing are helpful to identify this tumor, which may be eligible for ALK inhibitor-targeted therapy.

Embryonal Origin of Metanephric Adenoma and its Differential Diagnosis

BACKGROUND/AIM

The association of Wilms' tumor (WT), papillary renal cell tumor (PRCT) and mucinous tubular and spindle cell carcinoma (MTSCC) with embryonal rests has already been documented, but the cellular origin of metanephric adenoma (MA) is not yet known. The aim of this study was to understand their developmental evolution and find diagnostic markers.

MATERIALS AND METHODS

CD57, KRT7, AMACR, SCEL, WT1 and CDH17 expression was analysed by immunohistochemistry in the four types of tumors and the associated pre-neoplastic lesions.

RESULTS

Immunohistochemistry was able to differentiate WT, MA, MTSCC and PRCT. A phenotypic correlation between MA and perilobar nephrogenic rest associated with WT was identified.

CONCLUSION

Perilobar nephrogenic rest and MA arise from differentiation arrested cells of the proximal domain of the S-shape body. We propose that WT1, MA, MTSCC and PRCT derive from different forms of maturation arrested embryonal rests.

Novel clinicopathological and molecular characterization of metanephric adenoma: a study of 28 cases

Background

Metanephric adenoma is a rare, benign renal neoplasm with occasional misdiagnosis. However, its molecular characterization is not fully understood.

Methods

In this study, we use the hybrid capture-based Next-Generation Sequencing to sequence a panel of 295 well-established oncogene or tumor suppressor genes in 28 cases of MA patients in China. Novel clinicopathological markers associated with the mitogen-activated protein kinase (MAPK) pathway in metanephric adenoma were detected by immunohistochemistry.

Results

It was found that except for BRAF (22/28) mutations (c.1799 T > A, p.V600E), NF1 (6/28), NOTCH1 (5/28), SPEN (5/28), AKT2 (4/28), APC (4/28), ATRX (3/28), and ETV4 (3/28) mutations could also be detected. Meanwhile, a novel and rare gene fusion of STARD9-BRAF, CUX1-BRAF, and LOC100507389-BRAF was detected in one MA patient. In addition, although MEK phosphorylation was normally activated, the phosphorylation level of ERK was low in metanephric adenoma cases. Highly expressed p16 and DUSP6 may have contributed to these results, which maintained MA as a benign renal tumor.

Conclusions

This study provides novel molecular and pathological markers for metanephric adenoma, which could improve its diagnosis and increase the understanding of its pathologic mechanism.

Electronic supplementary material

The online version of this article (10.1186/s13000-018-0732-x) contains supplementary material, which is available to authorized users.

[All large necrotic and hemorrhagic kidney tumors in children are not necessarily malignant: A case of a 7-month-old child]

We report the case of a large tumor in the left kidney with necrotic and hemorrhagic features in a 7-month-old child, which was clinically and radiologically suggestive of a nephroblastoma. The tumor was a nodular mass measuring 8cm in diameter occupying two thirds of the kidney and presenting areas of necrosis and hemorrhage. No capsular rupture or renal sinus infiltration were found. Adjacent renal parenchyma appeared mascroscopically normal. Histologically, the tumor showed a strictly tubulopapillary architectural pattern with numerous psammomas. The initial hypothesis was a purely epithelial nephroblastoma. However, this hypothesis was rejected due to some immunohistochemical and histological characteristics and the final diagnosis was a metanephric adenoma. Metanephric adenoma is an exceptionally rare benign renal tumor in children. However, pathologists need to keep it in mind because simple surgical excision is curative.

A novel cytogenetic and molecular characterization of renal metanephric adenoma: Identification of partner genes involved in translocation t(9;15)(p24;q24)

Renal metanephric adenoma (MA) is a rare benign tumor frequently misclassified when microscopic features alone are applied. The correct classification of a renal tumor is critical for diagnostic, prognostic, and therapeutic purposes. Despite the advancements in cancer genomics, up until recently relatively few genetic alterations critical to MA development have been recognized. Recent data suggest that 90% of MA have BRAF^V600E mutations; the genetics of the remaining 10% are unclear. To date, only one case of a chromosomal translocation, t(9;15)(p24;q24) associated with MA has been reported. However, the potential role of the KANK1 gene, which lies near the breakpoint of the short arm of chromosome 9p24, in the etiology of MA was not examined. We identified the same cytogenetic aberration utilizing molecular cytogenetic techniques in a 22-year-old female patient, and further investigated the genes involved in the translocation that might have contributed to tumorigenesis. A series of fluorescence in situ hybridization (FISH) probes identified the rearranged genes to be KANK1 on chromosome 9 (9p24.3) and NTRK3 on chromosome 15 (15q25.3). Mate-Pair genome sequencing validated the balanced translocation between 9p24.3 and 15q25.3, involving genes KANK1 and NTRK3, respectively. BRAF^V600E mutational analysis was normal. Our findings indicate that gene fusions may be one mechanism by which functionally relevant genes are altered in the development of MA. Molecular and cytogenetic analyses have elucidated a novel genetic aberration, which helps to provide a better understanding of this genomic change and assist in diagnosis and classification of new subgroups/entities in metanephric adenomas.

The findings of CT and MRI in patients with metanephric adenoma

Background

Metanephric adenoma (MA) is a benign renal tumor that is difficult to distinguish from a malignant tumor via traditional radiography. The diagnosis of MA is often dependent on postsurgical histopathological examination. In the present report, the imaging features of MA on computer tomography (CT) and magnetic resonance imaging (MRI) were retrospectively evaluated.

Methods

Eight MA patients, 17–67 years of age, were pathologically confirmed and recruited between April 2009 and November 2014. Four of the eight patients were female. All patients underwent CT scanning, and one patient underwent MRI scanning. Three patients underwent CTA of the renal arteries. All patients underwent resection surgery (radical nephrectomy in five and nephron-sparing surgery in three patients).

Results

The average tumor size was 44.0 ± 23.6 mm. The lesions in 87.5 % cases were located both in the renal cortex and medulla and exhibited exophytic growth. Plain CT showed that MA tumors were solid, and the average CT value was 37.9 ± 6.7 HU. Dynamic contrast-enhanced CT revealed that enhanced degrees of MA tumors in the renal cortex, renal parenchymal, and pelvic phase were all lower than that of normal renal parenchyma. A slight enhancement in the renal cortex phase and an even higher enhancement in the renal parenchymal phase were observed in seven of the cases. Progressive enhancement in the pelvic phase was found in five cases and a slight decreased enhancement in the pelvic phase in two cases. MRI revealed that MA tumor was isointense on T1WI and isointense on T2WI with some slightly hyperintense areas in the center. CTA of the renal arteries revealed the nutrient artery in one patient and no nutrient artery in two. Immunohistochemical experiments demonstrated that most tumor cells were positive for vimentin, CK, and EMA.

Conclusions

MA is a rare benign renal neoplasm. Detailed knowledge of the CT and MRI characteristics of MA plays an important role in MA diagnosis and treatment.

A Case of Metanephric Adenoma and Acute Myocardial Infarction

Metanephric adenoma (MA) is a rare neoplasm that acounts for 0.2% of adult renal neoplasms. MAs are typically discover incidentally during detailed examinations for nonspecific symptoms such as abdominal or flank pain, hematuria, fever and palpable abdominal mass. Additionally, polycythemia has occasionally been reported as well. Herein we describe a case of metanephric adenoma which was an incidental finding in the course of a clinical autopsy in a patient with complete AV block and polycythemia. Histologically, the tumor was composed of small and uniform tubular structures reminiscent of renal tubuli, without signs of cellular atypia and pleomorphism. Such tumor histomorphology was consistent with the diagnosis of metanephric adenoma. Thrombosis is a common complication of polycythemia that often causes death. Polycythemia with an increasing number of blood cells causes hyperviscosity and, in 20-40% of cases, lethal thrombosis or hemorrhage. Hyperviscosity and coronary artery disease in our patient caused acute myocardial infarction with the subsequent rupture of posterior left ventricle wall and hemopericardium.

Retroperitoneal laparoscopic partial nephrectomy for treatment of metanephric adenoma (Report of 6 cases)

Objectives

To investigate the clinical and pathological features of metanephric adenoma (MA) and the clinical outcome after retroperitoneal laparoscopic nephron-sparing surgery.

Methods

Six out of 183 partial nephrectomies performed during January 2009 to August 2014 were confirmed to be MA confirmed by postoperative pathological study. Perioperative parameters of the six patients were then retrospectively collected, analyzed and compared with current literature, including warm ischemia time (WIT), total operation time, estimated blood loss (EBL), positive surgical margin (PSM), and complications. Surgical and oncological outcome of all six patients were evaluated based on a mean follow up of 17 months (5–48 months).

Results

Tumors in all six cases were all successfully removed by partial nephrectomy. Mean WIT was 24.7 min (19–35 min). Mean operation time was 103.6 min (82–147 min). Mean EBL was 53.5 ml (20–85 ml). No conversion, transfusion or other major complication were observed in all six cases. Postoperative pathology confirmed negative surgical margin in all six cases. During a mean of 17 month follow up (5–48 months), no local recurrence or metastasis were found in all six cases.

Conclusion

MA is a rare benign primary kidney epithelial cancer, which could hardly be differentiated from renal malignancies based on preoperative imaging. Our data suggested that retroperitoneal laparoscopic partial nephrectomy can be used for surgical treatment of MA, in terms of tumor control and preservation of renal function.

Prominent apical cytoplasmic bleb formation in metanephric adenoma: report of a case

In a case of metanephric adenoma of the kidney, many apical cytoplasmic blebs were found on the luminal surface of tumor cells. The tumor, measuring 15 mm in diameter, was found incidentally in the right kidney of a 40-year-old woman. It consisted of a dense proliferation of cuboidal cells forming small tubules of round or irregular shape. The apical portion of the cytoplasm of tumor cells exhibited club-shaped expansion or dome-like protrusion which was largely occupied by numerous free ribosomes. The neck portion of the protruded apical cytoplasm was constricted, and the apical cytoplasm appeared to have been "pinched-off" and shed into the lumen. The prominent formation of apical cytoplasmic blebs has, to our knowledge, not been documented in renal tumors except in angiomyoadenomatous tumors. Its pathological significance is unknown, but it most likely represents a response of tumor cells to some hypoxic or toxic cellular injuries.

Immunohistochemical phenotype and molecular pathological characteristics of metanephric adenoma

To assess the clinicopathological, immunohistochemical and molecular features of metanephric adenoma (MA). Clinicopathologic data were obtained for 5 cases of MA with follow-up information. Specimens from these patients were stained by HE and immunohistochemistry for the detection of WT1, vimentin, S-100 protein, CK7, P504s, CD10 and renal cell carcinoma marker (RCC). Fluorescence in situ hybridization (FISH) was performed on 4 tumors. The patients included 1 male and 4 females, aged from 30 to 49 (mean=39) years. Tumor diameters ranged from 3 to 5.5 cm. Histologically, the tumors had tubular, papillary, or glomeruloid architectures, and were composed of cells with uniform and round nuclei, inconspicuous nucleoli, and high ratio of nucleus to cytoplasm. Nuclear polymorphism and mitotic figures were not observed. Immunohistochemically, they expressed WT1 (5/5), vimentin (5/5), S-100 (4/5), CK7 (2/5), P504s (2/5), and CD10 (1/5) and not RCC. FISH study was carried out on 4 metanephric adenoma cases, and no abnormalities were observed in chromosomes 3, 7, 17, and P16 gene of chromosomes 9. MA is an uncommon renal tumor. Its diagnosis depends on morphological, immunohistochemical and molecular features.

BRAF mutations in pediatric metanephric tumors

Metanephric neoplasms of the kidney are uncommon, and some cases are associated with papillary carcinoma. Most cases of metanephric adenoma occur in adults, with fewer than 25 cases reported in children, and metanephric adenofibroma is even less common. The few metanephric tumors studied at the genetic level have not shown the gains of chromosomes 7 and 17 commonly seen in renal cell carcinoma, suggesting that the carcinoma arising in this setting has a separate genetic origin from the adenoma. However, the assumption that this carcinoma has the same chromosome gains as sporadic renal cell carcinoma has never been validated. We studied 4 cases of metanephric tumors in children, including 1 metanephric adenofibroma with papillary carcinoma. The composite tumor was studied by single nucleotide polymorphism array and fluorescence in situ hybridization, with the adenoma and carcinoma components analyzed separately. No copy number alterations were detected in either component. A BRAF V600E mutation has been reported in most cases of metanephric adenoma in adults. We performed BRAF V600E immunostaining and sequencing in our 4 pediatric cases. Three cases had a BRAF V600E mutation including the composite tumor, with both the adenoma and carcinoma components showing the same mutation. This finding provides the first genetic evidence that these 2 tumors are biologically linked. Ten cases each of pediatric renal cell carcinoma and Wilms tumor were immunonegative. Thus, BRAF V600E immunostaining is a helpful marker for pediatric metanephric adenoma, and additional research is required on the possible role of this mutation in the development of renal carcinoma.

The clinical and CT imaging features of metanephric adenoma

BACKGROUND

Patients with metanephric adenoma have a good prognosis after undergoing total nephrectomy or local resection with kidney preservation. Accurate diagnosing is important for guiding clinical treatment. Only few previous case reports have been found focusing on the imaging findings of metanephric adenoma.

PURPOSE

To evaluate the multislice computed tomography (MSCT) imaging characteristics of metanephric adenoma.

MATERIAL AND METHODS

The imaging findings in eight patients with metanephric adenoma were studied retrospectively. MSCT was undertaken to investigate tumor location, size, attenuation, cystic or solid appearance, calcification, capsule sign, and enhancement pattern.

RESULTS

Tumors (mean diameter, 3.3 ± 1.0 cm) were solitary (8/8), solid (7/8) with cystic components (2/8), no calcifications (7/8), had a poorly-defined margin (8/8), were centered in the renal medulla (7/8), compressed the renal pelvis (3/8), and none had retroperitoneal lymph node metastasis. The attenuation of metanephric adenoma tumors was less or equal compared to the renal cortex or medulla on unenhanced CT (30.6 ± 2.6 vs. 36.3 ± 4.6 vs. 33.2 ± 3.9, P > 0.05), while tumor enhancement after administration of an contrast agent was lower than that of normal renal cortex and medulla during all phases (P < 0.05).

CONCLUSION

Metanephric adenoma tends to be a solitary, poorly defined margin, isodense or hypodense mass arising from the renal medulla with enhancement less than the cortex and medulla during all phases.