Unusual Malignant Solid Neoplasms of the Kidney: Cross-Sectional Imaging Findings

Abstract

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.

Keywords: Computed tomography; Kidney; Magnetic resonance imaging; Malignant tumors.

Fig. 1. Primitive neuroectodermal tumor of kidney.

Axial (A) and coronal (B) post-contrast computed tomography images demonstrate large masses (arrows) arising from left kidney. Kidney parenchyma is almost completely replaced by mass. Central hypodense area (arrowheads) represents necrosis.

Fig. 2. Liposarcoma of kidney.

Axial post-contrast computed tomography image of 67-year-old male with surgically proven liposarcoma of kidney shows non-specific contrast enhancement and well circumscribed mass in upper pole of left kidney (arrow) with no associated macroscopic fat.

Fig. 3. Malignant neuroendocrine tumor of kidney.

Axial post-contrast computed tomography image of 52-year-old male demonstrates contrast-enhanced lesion of left kidney (arrows) that was malignant neuroendocrine tumor. Punctate focus of calcification at medial edge of lesion (arrowhead) is renal stone in adjacent calyx.

Fig. 4. Renal leiomyosarcoma.

A. Axial post-contrast computed tomography image demonstrates hypoenhancing solid mass with well-defined lobulated margins (arrow). Axial (B) and coronal (C) T2-weighted magnetic resonance image (MRI) reveals low signal intense left renal mass (arrows). D. Renal mass (arrow) appears with low enhancement on contrast-enhanced fat saturated T1-weighted MRI.

Fig. 5. Renal synovial sarcoma.

Axial T1- (A) and T2-weighted (B) magnetic resonance image (MRI) demonstrate right renal mass with low signal-intensity and solid (arrows) and high signal-intensity cystic (arrowheads) components. High signal intensity in cystic portion of mass represents hemorrhagic or protein rich fluid. C. Coronal T2-weighted MRI reveals right renal mass (arrow) with peripheral cystic portion. D. Axial fat-saturated T1-weighted MRI demonstrates enhancement of solid portion (arrow) of renal synovial sarcoma.

Fig. 6. Malignant fibrous histiocytoma of kidney.

A. Unenhanced axial computed tomography (CT) image demonstrates well-defined solid mass (arrow) arising from left renal capsule. B. Contrast-enhanced axial CT image reveals heterogeneous enhancement in mass (arrow).

Fig. 7. Sclerosing fibrosarcoma of kidney.

Axial (A) and coronal (B) contrast-enhanced computed tomography scans show low-attenuated well-defined mass (arrow) arising from left kidney.

Fig. 8. Metastatic osteosarcoma in kidney.

Axial post-contrast computed tomography image of 19-year-old boy with metastatic osteosarcoma of lower extremity demonstrates large calcified metastatic deposit in right kidney (black arrow). Note calcified left adrenal (white arrow) and bilateral perinephric space (arrowheads) metastases.