E1918. Imaging of Uncommon Renal Masses and Mass-Like Conditions
  1. Sooyoung Martin; University Hospitals Cleveland Medical Center
  2. Kevin Kalisz; Duke University Medical Center
Renal masses and mass-like entities are commonly encountered at imaging, either due to direct symptoms or incidentally. While relatively few pathologies may account for a majority renal mass cases, the differential diagnosis is vast including neoplastic (either benign or malignant), infectious, and inflammatory etiologies. Additionally, common renal mass pathologies may be encountered in uncommon settings. While imaging features of these uncommon entities may overlap, certain imaging and clinical features may allow for accurate diagnosis of these less common pathologies.

Educational Goals / Teaching Points
The educational goals of this exhibit are to: -Review the differential diagnosis of neoplastic, infectious, inflammatory, and other conditions presenting as renal masses -Differentiate imaging features of common and uncommon renal masses -Incorporate appropriate clinical context and imaging findings to provide appropriate differential diagnoses for renal masses and mass-like lesions

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Table of Contents/Outline: 1. Introduction 2. Updated WHO classification of renal cell tumors 3. Key and distinctive imaging features of uncommon renal masses and mass-like conditions when compared to commonly encountered masses -Malignant renal cell tumors: -Common: clear cell RCC, papillary RCC (type I) -Uncommon: papillary RCC (type II), chromophobe RCC, collecting duct carcinoma, renal medullary carcinoma, Xp11 translocation carcinoma -Other solid/enhancing renal masses -Common: angiomyolipoma, oncocytoma, metastases -Uncommon: lymphoma, lymphangioma, sarcoma -Infectious and inflammatory renal masses: -Common: pyelonephritis, abscess (bacterial) -Uncommon: IgG4-related disease, sarcoidosis, Erdheim-Chester 4. Common masses in uncommon settings -Masses in renal fusion abnormalities -Masses in renal transplants

The differential diagnosis of a renal mass is broad and includes a spectrum of benign and malignant entities. Certain imaging and clinical features can help narrow this differential and suggest certain less common diagnoses. Recognition of features uncommon renal masses and mass-like entities is critical as this may dramatically alter the work-up and management of certain patients.