The prevalence of small renal masses (SRM) has risen, paralleling the increased usage of cross-sectional imaging. A large proportion of these SRMs are not malignant, and do not require invasive treatment such as nephrectomy. Therefore, differentation between early renal cell carcinoma (RCC) and benign SRM is critical to achieve proper management. This article reviews the radiological features of benign SRMs, with focus on two of the most common benign entities, angiomyolipoma and oncocytoma, in terms of their common imaging findings and differential features from RCC. Furthermore, the role of percutaneous biopsy is discussed as imaging is yet imperfect, therefore necessitating biopsy in certain circumstances to confirm the benignity of SRMs.
Abdominal Fat/pathology ; Adenoma, Oxyphilic/diagnosis/radiography/ultrasonography ; Angiomyolipoma/diagnosis/radiography/ultrasonography ; Carcinoma, Renal Cell/*diagnosis/radiography/ultrasonography ; Diagnosis, Differential ; Humans ; Kidney Neoplasms/*diagnosis/*radiography/ultrasonography ; Leiomyoma/diagnosis/radiography/ultrasonography

Here we report a case in a 41-year-old woman histologically proven cystic embryonal sarcoma of the kidney, with emphasis on the imaging findings and pathological features. A large lobulated solid mass in the cystically dilated pelvocalyceal region was accompanied with hydroureter as depicted on both ultrasound and contrast-enhanced CT images.
Adult ; Diagnosis, Differential ; Female ; Follow-Up Studies ; Humans ; Imaging, Three-Dimensional/methods ; Kidney/radiography/surgery/ultrasonography ; Kidney Neoplasms/*radiography/surgery/*ultrasonography ; Neoplasms, Germ Cell and Embryonal/*radiography/surgery/*ultrasonography ; Sarcoma/*radiography/surgery/*ultrasonography ; Tomography, X-Ray Computed/methods

PURPOSE: To identify size criteria for complex cystic renal masses that can distinguish renal cell carcinoma from benign cysts supplementing the Bosniak classification. MATERIALS AND METHODS: We reviewed the records of 97 patients who underwent surgery for complex cystic renal masses from January 2001 to April 2010. The pathological results were compared with the lesion sizes measured by preoperative computed tomography and other radiological features (contrast enhancement, irregularities of cyst walls and septa, and calcification) were also obtained for categorization according to the Bosniak renal cyst classification. RESULTS: Malignancy was significantly associated with cyst size (>2 cm), male gender, and younger patient age (<50 years). According to the Bosniak classification, there was no category I cyst, and all 8 category II cysts were benign. However, 3 of 18 (17%) category IIF cysts, 21 of 39 (54%) category III cysts, and 29 of 32 (90%) category IV cysts were malignant. All category IIF cysts were benign in patients older than 50 years of age. CONCLUSION: Many complex cystic renal masses smaller than 2 cm were benign. We suggest that lesion size should be taken into account when formulating treatment plans for complex cystic renal masses.
Adolescent ; Adult ; Age Factors ; Aged ; Carcinoma, Renal Cell/diagnosis/radiography ; Child ; Child, Preschool ; *Diagnosis, Differential ; Female ; Humans ; Infant ; Kidney Diseases, Cystic/*diagnosis/radiography ; Kidney Neoplasms/*diagnosis/radiography ; Male ; Middle Aged ; Sex Factors ; Tomography, X-Ray Computed ; Young Adult

Renal hemangioma is an uncommon benign tumor which usually causes painless or painful gross hematuria. Its preoperative diagnosis is extremely difficult or even impossible. We experienced three cases of renal hemangioma, located mainly at the pelvocalyceal junction or in the inner medulla. US demonstrated variable echogenecity, and CT revealed a lack of significant enhancement. Where there is gross hematuria in a young adult, especially when the renal mass located in the pelvocalyceal junction or inner medulla shows little enhancement on CT, renal heman-gioma should form part of the differential diagnosis.
Adult ; Case Report ; Diagnosis, Differential ; Hemangioma, Capillary/*radiography/*ultrasonography ; Hemangioma, Cavernous/*radiography/*ultrasonography ; Hematuria/etiology ; Human ; Kidney Neoplasms/*radiography/*ultrasonography ; Male ; Tomography, X-Ray Computed

PURPOSE: To investigate and distinguish the computed tomography (CT) characteristics of chromophobe renal cell carcinoma (chRCC) and renal oncocytoma. MATERIALS AND METHODS: Fifty-one patients with renal oncocytoma and 120 patients with chRCC, diagnosed by surgery between November 2005 and June 2015, were studied retrospectively. Two observers, who were urologists and unaware of the pathological results, reviewed the preoperative CT images. The tumors were evaluated for size, laterality, tumor type (ball or bean pattern), central stellate scar, segmental enhancement inversion, and angular interface pattern and tumor complexity. To accurately analyze the mass-enhancing pattern of renal mass, we measured Hounsfield units (HUs) in each phase and analyzed the mean, maximum, and minimum HU values and standard deviations. RESULTS: There were 51 renal oncocytomas and 120 chRCCs in the study cohort. No differences in clinical and demographic characteristics were observed between the two groups. A central stellate scar and segmental enhancement inversion were more likely in oncocytomas. However, there were no differences in ball-/bean-type categorization, enhancement pattern, and the shape of the interface between the groups. Higher HU values tended to be present in the corticomedullary and nephrogenic phases in oncocytomas than in chRCC. Receiver-operating characteristic curve analysis showed that the presence of a central stellate scar and higher mean HU values in the nephrogenic phase were highly predictive of renal oncocytoma (area under the curve=0.817, p<0.001). CONCLUSIONS: The appearance of a central stellate scar and higher mean HU values in the nephrogenic phase could be useful to distinguish renal oncocytomas from chRCCs.
Adenoma, Oxyphilic/pathology/*radiography ; Carcinoma, Renal Cell/pathology/*radiography ; Diagnosis, Differential ; Female ; Humans ; Kidney Neoplasms/pathology/*radiography ; Male ; Middle Aged ; Retrospective Studies ; Tomography, X-Ray Computed

OBJECTIVE: To describe computed tomography (CT) features of metastatic gallbladder (GB) tumors (MGTs) from various primary tumors and to determine whether there are differential imaging features of MGTs according to different primary tumors. MATERIALS AND METHODS: Twenty-one patients who had pathologically confirmed MGTs and underwent CT were retrospectively enrolled. Clinical findings including presenting symptoms, type of surgery, and interval between primary and metastatic tumors were recorded. Histologic features of primary tumor and MGTs including depth of invasion were also reviewed. Imaging findings were analyzed for the location and morphology of MGTs, pattern and degree of enhancement, depth of invasion, presence of intact overlying mucosa, and concordance between imaging features of primary and metastatic tumors. Significant differences between the histologies of MGTs and imaging features were determined. RESULTS: The most common primary tumor metastasized to the GB was gastric cancer (n = 8), followed by renal cell carcinoma (n = 4) and hepatocellular carcinoma (n = 3). All MGTs (n = 21) manifested as infiltrative wall thickenings (n = 15) or as polypoid lesions (n = 6) on CT, similar to the features of primary GB cancers. There were significant differences in the morphology of MGTs, enhancement pattern, enhancement degree, and depth of invasion according to the histology of primary tumors (p < 0.05). Metastatic adenocarcinomas of the GB manifested as infiltrative and persistently enhancing wall thickenings, while non-adenocarcinomatous metastases usually manifested as polypoid lesions with early wash-in and wash-out. CONCLUSION: Although CT findings of MGTs are similar to those of primary GB cancer, they are significantly different between the various histologies of primary tumors.
Adenocarcinoma/pathology/radiography/secondary ; Adult ; Aged ; Carcinoma, Hepatocellular/pathology/radiography/secondary ; Carcinoma, Renal Cell/pathology/radiography/secondary ; Carcinoma, Squamous Cell/pathology/radiography/secondary ; Diagnosis, Differential ; Female ; Gallbladder Neoplasms/pathology/*radiography/*secondary ; Humans ; Kidney Neoplasms/pathology ; Liver Neoplasms/pathology ; Male ; Melanoma/pathology/radiography/secondary ; Middle Aged ; Neoplasm Invasiveness/radiography ; Retrospective Studies ; Stomach Neoplasms/pathology ; *Tomography, X-Ray Computed

BACKGROUNDThere are relatively few reports focusing on clinical and multi-slice CT (MSCT) imaging findings of mucinous tubular and spindle cell carcinoma (MTSCC). Our study aimed to characterize the clinical and MSCT imaging features of MTSCC.

METHODSThe imaging findings in 17 patients with MTSCC by MSCT were retrospectively studied. MSCT was undertaken to investigate tumor location, size, density, cystic or solid appearance, calcification, capsule sign, enhancement pattern, and retroperitoneal lymph node metastasis.

RESULTSTumors (mean diameter, (3.9 ± 1.7) cm) were solitary (17/17), solid (16/17) with cystic components (5/17), had no calcifications (14/17), had a poorly defined margin (14/17), were centered in the medulla (15/17), compressed the renal pelvis (7/17), and neither lymph node nor distant metastasis was found. The attenuation of MTSCC tumors was equal to that of the renal cortex or medulla on unenhanced CT (32.3 ± 2.6, 36.3 ± 4.6, 33.2 ± 3.9, respectively, P > 0.05), while tumor enhancement after administration of a contrast agent was lower than that of normal renal cortex and medulla during all phases (P < 0.05).

CONCLUSIONMTSCC tends to be a solitary, isodense mass with poorly defined margin arising from the renal medulla with enhancement less than the cortex and medulla during all phases.

Adenocarcinoma, Mucinous ; diagnosis ; diagnostic imaging ; Adult ; Carcinoma ; diagnosis ; diagnostic imaging ; Carcinoma, Renal Cell ; diagnosis ; diagnostic imaging ; Female ; Humans ; Kidney Neoplasms ; diagnosis ; diagnostic imaging ; Male ; Middle Aged ; Radiography

Malignant kidney neoplasms are the most frequently encountered solid kidney masses. Although renal cell carcinoma is the major renal malignancy, other solid malignant renal masses should be considered in the differential diagnosis of solid renal masses that do not contain a macroscopic fatty component. In this pictorial essay, we present the imaging findings of a primitive neuroectodermal tumor, primary liposarcoma of the kidney, primary neuroendocrine tumor, leiomyosarcoma, synovial sarcoma, malignant fibrous histiocytoma, sclerosing fibrosarcoma and renal metastasis of osteosarcoma.
Bone Neoplasms/secondary ; Carcinoma, Renal Cell/pathology/radiography ; Diagnosis, Differential ; Fibrosarcoma/radiography ; Histiocytoma/radiography ; Humans ; Kidney Neoplasms/*pathology/radiography ; Leiomyosarcoma/pathology/radiography ; Magnetic Resonance Imaging ; Middle Aged ; Neuroectodermal Tumors, Primitive/pathology/radiography ; Osteosarcoma/pathology ; Sarcoma ; Sarcoma, Synovial/radiography ; Tomography, X-Ray Computed

A 61-year-old man presented with a right renal mass with a vena caval thrombus on computed tomography that was consistent with renal cell carcinoma. The results of routine laboratory examinations and urinalysis were within normal limits. Preoperative planning was critical owing to the presence of the vena caval thrombus. A radical nephrectomy, vena caval thrombectomy, and regional lymphadenectomy were done. The pathologic report was consistent with a high-grade, invasive urothelial carcinoma, with sarcomatoid differentiation involving the renal vein and inferior vena cava (Stage IV, T4N0M0). Thus, this was a rare case of upper tract urothelial carcinoma. Adjuvant chemotherapy with the methotrexate, vinblastine, doxorubicin, cisplatinum regimen is scheduled. To our knowledge, this is the first report in Korea of upper tract urothelial carcinoma of the sarcomatoid type with a vena caval thrombus.
Carcinoma, Renal Cell/pathology ; Diagnosis, Differential ; Humans ; Kidney Neoplasms/diagnosis/*pathology ; Lymph Node Excision/methods ; Male ; Middle Aged ; Nephrectomy/methods ; Renal Veins/*radiography ; Thrombectomy/methods ; Thrombosis/*radiography ; Tomography, X-Ray Computed ; Vena Cava, Inferior/*radiography

A 61-year-old man presented with a right renal mass with a vena caval thrombus on computed tomography that was consistent with renal cell carcinoma. The results of routine laboratory examinations and urinalysis were within normal limits. Preoperative planning was critical owing to the presence of the vena caval thrombus. A radical nephrectomy, vena caval thrombectomy, and regional lymphadenectomy were done. The pathologic report was consistent with a high-grade, invasive urothelial carcinoma, with sarcomatoid differentiation involving the renal vein and inferior vena cava (Stage IV, T4N0M0). Thus, this was a rare case of upper tract urothelial carcinoma. Adjuvant chemotherapy with the methotrexate, vinblastine, doxorubicin, cisplatinum regimen is scheduled. To our knowledge, this is the first report in Korea of upper tract urothelial carcinoma of the sarcomatoid type with a vena caval thrombus.
Carcinoma, Renal Cell/pathology ; Diagnosis, Differential ; Humans ; Kidney Neoplasms/diagnosis/*pathology ; Lymph Node Excision/methods ; Male ; Middle Aged ; Nephrectomy/methods ; Renal Veins/*radiography ; Thrombectomy/methods ; Thrombosis/*radiography ; Tomography, X-Ray Computed ; Vena Cava, Inferior/*radiography