David S. Hartman

Cystic renal cell carcinoma

Cystic renal cell carcinoma includes any malignant neoplasm of renal tubular epithelium which presents as a fluid-filled mass. Approximately 15 per cent of cases of renal cell carcinoma will be cystic on radiologic and pathologic examination. The clinical features of cystic renal cell carcinoma are similar to those which are solid. The radiographic and pathologic findings of cystic renal cell carcinoma are often more confusing and less specific than the findings of renal cell carcinoma which are predominantly solid. There are four basic pathologic mechanisms resulting in cystic renal cell carcinoma: intrinsic multiloculated growth; intrinsic unilocular growth (cystadenocarcinoma); cystic necrosis; and origin from the epithelial lining of a preexisting simple cyst. There are three basic radiologic patterns of cystic renal cell carcinoma: unilocular cystic mass, multiloculated cystic mass, and discrete mural nodule in a cystic mass. Cystic renal cell carcinoma is often extremely difficult to differentiate from non-neoplastic, benign neoplastic, and other malignant neoplastic masses utilizing radiologic studies alone. This review presents the clinical, pathologic, and radiographic features of cystic renal cell carcinoma and discusses its radiologic differential diagnosis.

Cystic renal masses: Usefulness of the bosniak classification

To determine the usefulness of the Bosniak classification of cystic renal masses, the computed tomographic (CT) and ultrasound findings of 16 pathologically proven cystic renal masses were retrospectively reviewed. All imaging studies were reviewed and categorized utilizing the Bosniak classification without knowledge of the final pathologic diagnosis. There were no category I lesions (classical simple cyst), four category II (minimally complicated), seven category III lesions (more complicated), and five category IV lesions (probable malignant). All category II lesions were benign, all category IV lesions were malignant. Of the seven category III lesions, three were benign and four were malignant. We conclude that the Bosniak classification is extremely useful in the management of cystic renal masses.

Renal cystic diseases

Abstract Renal cystic disease comprises a mixed group of heritable, developmental, and acquired disorders. Because of their diverse etiology, histology, and clinical presentation, no single scheme of classification has gained acceptance. Conditions include autosomal dominant polycystic kidney disease, acquired renal cystic disease, medullary sponge kidney, autosomal recessive polycystic kidney disease, multicystic dysplastic kidney, medullary cystic disease, tuberous sclerosis, cysts of the renal sinus, and von Hippel-Lindaus disease. An awareness of the pathology of each cystic disease is helpful in the understanding of the corresponding radiological images. Imaging techniques used in evaluating renal cystic disease include intravenous urography, sonography, CT, MRI, nuclear medicine, and renal angiography. Many types of cystic disease show similar imaging features. Meticulous attention to subtle radiological findings is therefore essential for reaching a correct diagnosis. Imaging features requiring analysis include whether the cysts are unilateral or bilateral, renal size and functional status, cyst distribution in the kidneys, and the presence of hemorrhagic and calcified renal cysts, solid renal masses, renal sinus cysts, and cysts in adjacent organs. Radiological findings should be carefully correlated with clinical features such as patient age, family history, symptoms, physical findings, and renal functional status before a diagnosis is attempted.

Primary Malignant Renal Tumors in the Second Decade of Life: Wilms Tumor Versus Renal Cell Carcinoma

Primary renal malignancies occur least frequently in the second decade of life. Of the 4,798 cases of renal cell carcinoma and Wilms tumor referred to the Armed Forces Institute of Pathology 53 renal cell carcinomas and 56 Wilms tumors occurred in the 10 to 20-year age group. Pathologically, both tumors in this age range are similar to those occurring at a more typical age, and histologic differentiation between renal cell carcinoma and Wilms tumor is seldom a problem. While radiographic evaluation is useful to characterize the neoplasm, evaluate the contralateral kidney and detect the presence of tumor extension, current imaging techniques cannot confidently distinguish these 2 tumors.

Computed tomography of renal tuberculosis and its pathological correlates

Computed tomographic studies of eight patients with proven renal tuberculosis demonstrated a spectrum of findings related to the extent and the severity of kidney involvement. In early or focal disease, obstruction of a single major calyx or a group of minor calyces was noted (four cases) with no excretion of contrast material into the affected calyces (three cases) and cortical thinning. Tuberculosis of the renal pelvis (five cases) was manifested by either pelvic dilatation secondary to ureteropelvic junction obstruction (three patients) or diffuse pelvic contraction (two patients). In far advanced disease (four cases) the kidneys were small and exhibited atrophy with replacement of parenchyma by one or more low density areas. Calcifications (37.5%) were identified in the parenchyma and within the calyces. Computed tomography may provide the first clue in suggesting the inflammatory nature of a renal mass and excluding a neoplastic process. Computed tomography is also of value in determining the full extent of extrarenal involvement and the amount of residual functioning parenchyma, both of which are critical in proper treatment planning.

CURRENT CONCEPTS AND CONTROVERSIES IN IMAGING OF RENAL CYSTIC DISEASES

Renal cystic disease compromises a diverse group of inherited and acquired entities. This article reviews the clinical, pathologic, and radiologic findings of eight renal cystic diseases. For each entity, the current concepts of pathogenesis and pathophysiology are discussed. When appropriate, controversies concerning terminology, management, and malignant potentials are addressed. Renal cystic diseases that are discussed include autosomal dominant and autosomal recessive polycystic kidney disease, medullary sponge kidney, medullary cystic disease, multicystic, dysplastic kidney, von Hippel-Lindau disease, acquired cystic kidney disease, and tuberous sclerosis.

Xanthogranulomatous pyelonephritis: sonographic--pathologic correlation of 16 cases.

Xanthogranulomatous pyelonephritis (XGP) is an uncommon renal inflammatory disease characterized by the destruction and replacement of normal parenchyma by sheets of lipid‐laden histiocytes. The process may be diffuse or segmental. Sonograms of 16 cases of XGP (13 diffuse, three segmental) were retrospectively reviewed and correlated with their pathologic findings. The typical case of diffuse XGP demonstrates the following: renal enlargement, replacement of normal architecture by multiple fluid‐filled masses, pelvic contraction or only moderate separation of the central echo complex, and a pelvic calculus. Although most cases have a large staghorn calculus, its sonographic demonstration may be difficult, perhaps as a consequence of peripelvic fibrosis. Atypical cases of diffuse XGP mimic pyelonephrosis with massive hydronephrosis and fluid‐‐debris levels. In these atypical cases, a staghorn calculus is often conspicuously absent. Segmental XGP is recognized as an area of parenchymal destruction surrounding one calyx or one pole of duplication. Segmental XGP should be distinguished from focal xanthogranulomatous inflammation of the kidney, which is a distinct pathologic entity (cortical location, no pelvic communication, absent pyelitis). When typical gross pathologic features are present, sonography should make possible accurate identification of diffuse and segmental XGP.

The Varied Radiographic Manifestations of Retroperitoneal Malignant Fibrous Histiocytoma Revealed through 27 Cases

Malignant fibrous histiocytoma, a pleomorphic sarcoma, represents the most common soft tissue sarcoma of late adult life. Approximately 15 per cent of the cases of malignant fibrous histiocytoma arise within the abdominal cavity or retroperitoneum. Although tumors in this series arose in many different sites, their proximity to the kidney necessitated a nephrectomy in 44 per cent of the cases (12 of 27). In 3 cases calcification was noted, which varied from a few small speckled areas to extensive large, coarse densities. The masses tended to compress or displace adjacent structures and vessels radiographically. Renal, duodenal and cecal invasion occasionally occurred. Ultrasonically, most tumors were hypoechoic (9 cases), with a few having a mixed pattern (2). On computerized tomography the masses were well circumscribed, with computerized tomography numbers in the range of solid tissue except for a few small areas of decreased density. The vascularity was variable, with 8 tumors being hypovascular and 8 showing a moderate to hypervascular pattern. Interestingly, the tumor derived a part of its blood supply from the renal vasculature in 12 cases (44 per cent). Even though malignant fibrous histiocytoma often was diagnosed incorrectly as an intrarenal or adrenal neoplasm, a cleavage plane usually could be identified between the tumor and the renal parenchyma in 1 of the studies, especially on the angiogram. This finding suggested its extrarenal origin. Knowing the tendency of malignant fibrous histiocytoma to arise from or be physically near the kidney and/or adrenal gland in elderly men may be of some diagnostic value.

The CT appearance of Wilms Tumor

The computed tomographic (CT) findings in 30 Wilms tumors in 25 patients were reviewed and correlated with the pathological findings. Most tumors were quite large at the time of detection (average diameter 11 cm) and were cortical in origin. Peripheral lesions tended to grow exophytically. On the noncontrast studies an inhomogeneous mass with low-density areas (tumor necrosis) was seen. Small, focal calcifications (13.3%) and fat (6.9%) were much more readily identified with CT than with intravenous pyelography. After contrast medium injection, slight enhancement of the tumors was noted, and foci of necrosis became more prominent. A sharp demarcation between the tumor and normal parenchyma (seen in 19 cases) correlated with the pseudocapsule that is often present. Particularly striking was the presence of a persistent, ellipsoid area of increased attenuation corresponding to the compressed uninvolved renal parenchyma seen in 14 cases. Two cases were seen with complete tumor infiltration of the kidney pathologically and on CT. The primary clinical usefulness of CT in Wilms tumor is to detect multiple masses, to determine the extent of tumor, and to evaluate the opposite kidney.

Scar sign of renal oncocytoma: magnetic resonance imaging appearance and lack of specificity

This case report illustrates the magnetic resonance imaging (MRI) appearance of a typically asymptomatic renal oncocytoma as a homogeneous mass of medium signal with a stellate central region of decreased signal, representing the central scar. The MRI was correlated with computed tomography (CT), ultrasound (US), and gross pathologic appearance. The appearance of a central scar is not specific for oncocytoma and does not exclude renal cell carcinoma, as illustrated by a second case.