Panlobar nephroblastomatosis with cystic dysplasia: an unusual case with diffuse renal involvement studied by immunohistochemistry

Unusual association of Wilms' tumor with cystic diseases of kidney: A pathologic surprise

Wilms' tumor (or nephroblastoma) is the most common renal malignancy in the pediatric population which consists of blastemal, epithelial, and stromal elements in variable proportions. The occurrence of renal cysts in children and infants is a rare phenomenon and is possibly an outcome of developmental aberrations in mesonephric blastema. The coincidental association of nephroblastoma with renal cysts is a very rare finding. Here, we describe two cases of Wilms' tumor with an unusual association between glomerulocystic kidney disease and multicystic dysplastic kidney.

Perilobar nephroblastomatosis: natural history and management

Nephroblastomatosis (NB) has been considered as a precursor of Wilms tumor (WT). The natural history of NB seems to present significant variation as some lesions may regress spontaneously, while others may grow and expand or relapse and develop into WT later in childhood. Although, most investigators suggest adjutant chemotherapy, the effect and duration of treatment are not well established. Children with diffuse perilobar NB, Beckwith-Wiedemann syndrome, and hemihypertrophy seem to particularly benefit from treatment. We discuss our experience on two cases of NB and we review the literature for the management of this rare condition.

Neoplastic and proliferative disorders of the perinephric space

The perinephric space is a well-marginated central compartment of the retroperitoneum, located between the anterior and posterior pararenal spaces. Various neoplastic and proliferative disorders can affect the perinephric space, and there is a wide array of imaging findings. Although many perinephric lesions may extend directly from the kidney and adrenal gland, other lesions occur in the perinephric space due to haematogenous spread, as part of a systemic disease, or by extension from an adjacent retroperitoneal compartment. Imaging plays a pivotal role in the diagnosis of perinephric diseases, as many of the disease processes affecting this space will not result in clinical signs or symptoms until the disease is at an advanced stage. Despite the often shared non-specific clinical and imaging findings among these disease processes, application of a categorical differential diagnosis based on the imaging characteristics will serve to narrow the differential diagnosis and direct further evaluation and treatment. In this article, the lesions have been categorized as soft-tissue rind [nephroblastomatosis, fibrosis, Erdheim-Chester disease (ECD), extramedullary haematopoiesis, lymphoma, infiltrating metastases], focal solid lesions (extension of renal or adrenal malignancies, melanoma metastases, treated lymphoma), fat-containing lesions (angiomyolipoma, liposarcoma, myelolipoma), and cystic lesions (lymphangiomas, abscesses). The aim of this article is to demonstrate and describe the key imaging features of several neoplastic and proliferative disorders that affect the perinephric space.

Bilateral universal nephroblastomatosis in an 8-month-old infant treated with chemotherapy

We report the case of an 8-month-old female infant presenting with bilateral, diffusely enlarged kidneys. A diagnosis of bilateral, universal nephroblastomatosis was made on tissue biopsies from both kidneys after correlation with the radiological findings. As far as we know, this is the oldest patient reported with this diagnosis in the English literature (they are usually younger than 4 months). The patient was treated with chemotherapy with very good response and almost 1 year later she is showing no signs of recurrence of her disease.

Renal cystic neoplasms and renal neoplasms associated with cystic renal diseases: pathogenetic and molecular links

Cystic renal neoplasms represent an isolated cystic mass not accompanied by cystic change of the renal parenchyma. Although cystic change may be seen in any type of renal neoplasm, a few (i.e., cystic renal cell carcinoma, cystic nephroma, cystic partially differentiated nephroblastoma, mixed epithelial and stromal tumor) are characterized by constant cystic change that may involve the entire tumor. Cystic kidney disease is characterized by cystic change, which usually involves the kidneys in a bilateral and diffuse pattern, does not create a discreet mass, and is due to hereditary or developmental conditions. Some of the cystic kidney diseases are not known to give rise to renal neoplasm; others such as autosomal polycystic kidney disease or multicystic dysplastic kidney may fortuitously coexist with renal neoplasms. Three conditions (acquired cystic kidney disease, tuberous sclerosis, and von Hippel-Lindau disease) are associated with renal neoplasms with such a high frequency that they are considered preneoplastic. This article reviews the differential diagnoses among cystic neoplasms. It also focuses on the underlying genetic and molecular mechanisms for the relationship between cystic renal diseases and renal neoplasms.

Clinicopathologic features of nephrogenic rests and nephroblastomatosis

Nephrogenic rests are the consequence of residual metanephric tissue in a fully developed kidney. They usually occur along the perimeter of a mature renal lobe (i.e., perilobar), within the lobe itself (i.e., intralobar), or both (i.e., combined). Nephrogenic rests can be grossly obvious or microscopically discrete. Nephroblastomatosis designates nephrogenic rests that are multifocal or diffuse, and implies more extensive disease. Universal (panlobar) nephroblastomatosis denotes complete replacement of the renal lobe by nephrogenic tissue. The fate of nephrogenic rests and nephroblastomatosis varies and includes obsolescence, sclerosis, dormancy, hyperplasia, or neoplasia. Evidence strongly suggests that neoplastic transformation of nephrogenic rests results in Wilms' tumor (nephroblastoma). Nephrogenic rests almost always occur in the setting of Wilms' tumor; perilobar rests show a strong association with synchronous bilateral Wilms' tumors, whereas intralobar rests are more strongly associated with metachronous tumors. Genetic studies have shown that nephrogenic rests often share many of the same chromosomal defects as Wilms' tumor, which provides further evidence that they are precursors to nephroblastoma. Thus, nephrogenic rests are recognized as clinically significant entities requiring adequate detection and close surveillance. Heightened awareness regarding the clinical relevance of nephrogenic rests and nephroblastomatosis (1) has led to improved detection of these precancerous lesions, (2) fostered more intensive investigation into their biologic behavior, and (3) initiated in-depth discussions about potentially new treatment regimens. The pathologists' ability to identify and detect nephrogenic rests has benefited from the more efficient Beckwith classification. Radiologists have deployed high-resolution radiologic/imaging modalities to improve detection of nephrogenic rests in situ. Clinicians and surgeons are more aware of the impact that nephrogenic rests have upon patient management. Despite this progress, more data is needed to further define these lesions.

Intrarenal cystic mass with pelviureteral junction obstruction

An abdominal mass in the first year after birth most commonly originates from the kidney. Renal masses in this age group are often cystic and may be associated with other abnormalities. We describe an unusual benign unilateral cystic lesion and coexisting pelviureteral junction obstruction in a newborn male with an otherwise morphologically and functionally normal urinary tract. A near normal kidney resulted from subsequent resection of the cyst wall combined with pyeloplasty.

Multinodular hyperplastic pannephric nephroblastomatosis with tubular differentiation: a new morphologic variant

We report a case of bilateral nephromegaly detected prenatally with oligohydramnios. Delivered at 35 weeks, this black male infant rapidly developed renal failure, requiring dialysis. He lived 3 1/2 months. The kidneys were three times normal size and diffusely multinodular, with hypoplastic calyces, no corticomedullary demarcation, and no pyramids. Histologically, they revealed hyperplastic embryonal rests composed of tubules and ducts with prominent branching. The nodular rests were intermixed with areas of mature parenchyma, which showed prominent oxalosis. By flow cytometry, rests were diploid, with an S-phase fraction of 25.9%. The proliferation of embryonal collecting system analogs is attributed to excessively rapid and prolonged branching of the ureteric bud, dating from the fourth gestational month or earlier. This unique case may represent a new morphologic variant of universal nephroblastomatosis.

Proliferation and maturation indices in nephrogenic rests and Wilms tumor; the emergence of heterogeneity from dormant nodular renal blastema

Independent nephrogenic rests (NRs) accompany many Wilms tumors (WTs), exhibit a range of qualities suggesting dormancy, maturation, regression, and hyperplasia, and may carry the WT-1 mutation. We assessed nucleolar organizer regions, proliferating cell nuclear antigen (PCNA) activity, cytoplasmic filament expression, and nuclear morphology in 79 nephrogenic rests accompanying 20 WTs. We found a direct relationship between the size of a blastematous NR and the AgNOR number per nucleus and a close correlation with PCNA activity. The blastema of most NRs > 1 cm in diameter was indistinguishable from blastema of most WTs. The smallest NR usually had a low number of silver-reactive nucleolar organizing regions (AgNORs), low PCNA activity, and absent cytoplasmic filaments, all characteristics of a nascent dormant state in which both proliferation rate and protein synthetic activity are low. Intermediate filament expression was variable in blastema of larger NRs; cytoplasmic filaments correlated with emergence of epithelial maturation and absence of filaments with accumulation of immature cells; mature epithelial structures in NRs had low AgNOR number and PCNA activity representing a terminal dormant state. The majority of blastemal cells in most WTs and in one-third of large hyperplastic NRs lack cytoplasmic filaments. This, plus the occasional finding in large NRs of features more typical of WTs such as prevalence of apoptosis, patches of frank necrosis, multinodular architecture, and expanses of monomorphic, poorly vascularized blastema with low PCNA activity, suggest that it may be possible to distinguish NRs that are progressing toward WT from those that are merely hyperplastic. This study refines the concepts of dormancy and hyperplasia as expressed in NRs and provides a general framework for probing the relationship of molecular events to progression of a small proportion of NRs to WT. Criteria used herein to define dormancy and hyperplasia may be useful in assessing lesions other than typical WT, such as unusually large or extensive NRs or uncommon differentiated WTs where the potential for aggressive behavior may be lower than in usual WTs.