Nephroblastoma, Upper Pole vs. Renal Cyst

Left picture: The diagnosis is a nephroblastoma of the upper pole with exophytic growth. The mass is firm on palpation. The mass has been removed by nephrectomy because the malignant tumor and the intrarenal expansion has been diagnosed preoperatively with certainty by radiological imaging with ultrasound and CT. Right picture: Here, a renal cyst, not a malignant tumor, is present which became a space-occupying mass due to a constant increase in size. The mass is covered by a seam of kidney tissue and is tense and cystic on palaption. Such findings on palpation may also occur in Wilm´s tumor following hemorrhage or tumor necrosis with liquefaction. In spite of progress in radiological imaging the surgeon is faced again and again with situations in which an equal or similar differential diagnosis is imposed, e.g. malignancy versus malformation. In case of a renal cyst which can be split off, a nephrectomy is not indicated.

Left picture: At surgery of a toddler a mass of the upper pole is recognizable which is growing to the outside. The visible part of the residual kidney is not involved. Right picture: The operative findings in a schoolchild show the upper pole of the right kidney. A roundish mass is recognizable which differs from the residual normal kidney tissue concerning color, level and consistency.