Extensively cystic renal neoplasms: cystic nephroma, cystic partially differentiated nephroblastoma, multilocular cystic renal cell carcinoma, and cystic hamartoma of renal pelvis.

Predominantly cystic renal neoplasms have been the source of diagnostic confusion and controversy. In this review, the authors analyze the clinical and pathological features of four entities that consistently exhibit a diffusely cystic growth pattern, are strikingly similar in their gross appearances, and are not separable by preoperative imaging studies. Based on the literature, this review concludes that tumors in young children that have been classified as cystic nephroma and cystic partially differentiated nephroblastoma likely represent a single entity, and all should be considered highly cystic Wilms' tumors with little or no capacity for invasion or metastasis and diagnosed as cystic partially differentiated nephroblastoma. Conversely, cystic nephroma in adults has no discernible connection with Wilms' tumor or nephrogenic rests and should be considered a benign composite neoplasm of stroma and epithelium of unknown histogenesis, which may rarely become malignant with secondary development of a sarcoma. Multilocular cystic renal cell carcinoma appears to be unrelated to cystic nephroma and if the following criteria are met, it appears to be a neoplasm with an intrinsically cystic growth pattern, and no, or at most little, malignant potential: (1) an expansile mass is surrounded by a fibrous wall, (2) the interior of the tumor entirely is composed of cysts and septa with no expansile solid nodules, and (3) the septa contain aggregates of epithelial cells with clear cytoplasm. Cystic hamartoma of the renal pelvis is a rare, complex tumor composed of stroma with a prominent smooth muscle component and a variety of epithelial elements.

Lymphangioma of the kidney: a pathologic entity distinct from solitary multilocular cyst.

A case of primary renal lymphangioma is reported. This represents the first documented example of such a lesion confirmed by immunocytochemical and ultrastructural studies. Whereas previously regarded as synonymous terms, the recognition of lymphangioma as a pathologic entity distinct from solitary multilocular cyst of the kidney appears warranted. Although rare, lymphangioma should be considered in the differential diagnosis of multicystic lesions of the kidney.

Multilocular cystic renal cell carcinoma. Radiological diagnosis.

Multilocular cystic renal cell carcinoma (MCRCC), and its pathological characteristics and roentgenological and B-mode ultrasonographic appearances are described. MCRCC, a special renal carcinoma, can be divided into localized and diffused forms.

Multilocular renal cyst: electron microscopic evidence of pathogenesis.

Two cases of multilocular renal cyst (MRC) are presented with electron microscopic findings. The epithelial cells of the cysts resembled renal collecting tubule cells and not convoluted tubule or Henle's loop cells. Intercystic areas contained only connective tissue elements. Simple MRC appears to be a congenital malformation that results from segmental maldevelopment of the ureteric bud. In some cases of MRC, the intercystic septa contain immature renal elements. The lesion is then called cystic poorly differentiated nephroblastoma (CPDN). However, in both MRC and CPDN, local recurrence or metastases have not been described. Treatment of these lesions should consist of nephrectomy, careful histologic evaluation to rule out obvious foci of Wilms' tumor, and conservative follow-up.

Case report of a primary cystic sarcoma of the kidney, demonstrating fibrohistiocytic, osteoid, and cartilaginous components (malignant mesenchymoma).

The first case of a primary, cystic sarcoma of the kidney, containing fibrohistiocytic, osteoid, and cartilaginous elements (malignant mesenchymoma) is reported. The neoplasm occurred in a 29-year-old white woman, who had a right upper quadrant mass at least four years prior to presentation. Light and electron microscopy findings are presented. A 14-month follow-up revealed an extensive tumor recurrence in the right perirenal area with no apparent metastastic disease.

Multilocular cystic leiomyoma of the kidney.

A large, multilocular cystic mass from the kidney of a 26-year-old woman was examined by light microscopy and transmission electron microscopy. Ultrastructurally the cysts were shown to be lined by smooth muscle cells, giving evidence that the cysts originated in smooth muscle. Thus the tumor is considered to be a multilocular cystic leiomyoma, an apparently unique renal tumor.