Glomerulocystic kidney presenting as a unilateral kidney mass in a newborn with tuberous sclerosis: Report of a case and review of the literature.

Glomerular cysts are defined as a 2-3 times dilation of Bowman spaces and their presence in at least 5% of the glomeruli defines the kidneys as glomerulocystic (GCK). The association between cystic kidney disease and the tuberous sclerosis complex (TSC) is well known, but its presentation as a unilateral mass with glomerulocystic pattern is rare. We describe a case of an infant with a prenatal diagnosis of TSC, with a renal mass that was believed to be a renal tumor. A four-month-old infant with maternal history of TSC and prenatally diagnosed subependymal nodules and a right renal mass underwent nephrectomy. Histopathology revealed a segmental GCK with epithelial hyperplasia of the tubules and cysts. A diagnosis of TSC associated GCK was rendered. Eight other cases with similar histopathological findings were found in the literature, two of which presented as a localized mass. Usually there is no family history but the pathologic findings are similar. Awareness of the entity and its presentation as a localized mass may aid in the differential diagnosis of renal masses in infants. The pre-operative diagnosis of GCK is difficult and relies on a high degree of clinical awareness and imaging skills. Its presence should prompt the search for its etiology, particularly the exclusion of a heritable cause. The hyperplastic tubular epithelium within the glomerular cysts found in ours and other reported cases seems so characteristic that may serve as a major clue for the diagnosis of TSC.