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Roentgen Features of Renal Adenomas

1965; Radiological Society of North America; Volume: 84; Issue: 2 Linguagem: Inglês

10.1148/84.2.263

1527-1315

Jack G. Rabinowitz, Bernard S. Wolf, Richard H. Goldman,

Medical Imaging and Pathology Studies

Adenomas are common benign tumors of the kidney, occurring as single or multiple yellowish-grey nodules within the renal cortex immediately below the renal capsule. Reports of their incidence at necropsy vary from 0.08 per cent to 3.0 per cent (1, 2). In most instances they are small and incidental findings. The tumors of larger size cause a localized bulge of the renal surface and may also project into the parenchyma to distort the collecting system. Adenomas grow slowly, causing atrophy of the adjacent renal parenchyma which is replaced by connective tissue. This forms a well defined, fairly thick capsule completely surrounding the tumor. Numerous thin-walled venous channels and occasional remnants of renal tissue are encountered within the capsule (Fig. 1). Only a portion of the tumor circumference remains in contiguity with kidney parenchyma; the greater part of the tumor projects into the surrounding perirenal tissues (Fig. 2). Histologically, adenomas are divided into papillary, tubular, and alveolar types (3) and are subclassified on the basis of cytoplasmic-staining properties (4). Each type of neoplasm may be solid or cystic or have both elements. The vascular supply in most instances is quite modest and distinctly less than that seen in solid portions of malignant tumors (5). Papillary adenomas usually present as cysts into which multiple epithelium-covered stalks protrude. Tubular adenomas are characterized by the formation of elongated, irregular tubules lined by small cells with large nuclei. Alveolar adenomas are rare; histologically they resemble clear-cell renal carcinomas. The majority of adenomas of the kidney are asymptomatic and are discovered accidentally during clinical investigation for some other purpose. The absence of symptoms even with large tumors is presumably the result of their peripheral location and failure to infiltrate the collecting system. Occasionally, however, these tumors may present with symptoms of pain and hematuria. The hematuria in such cases apparently is not due to direct bleeding from the tumor but to secondary congestive changes of the vessels within the pelvis. The question of malignant transformation is still not completely resolved. Adenomas have been reported which showed little or no tendency to grow during a five-year interval (3, 8). Despite the typically benign histological appearance, however, many authors (3, 6) believe that metastases can occur following surgical extirpation and that therefore only autopsy proof warrants a benign designation. Buckley (7) has reported a benign tubular adenoma with areas of malignant transformation. There can be no doubt that some tumors will recur with dissemination or demonstrate metastases originally despite a definitely benign histological picture. This was shown in one of our cases in which a renal mass was diagnosed as a benign papillary adenoma following resection.