The Differential Diagnosis of Medullary-Based Renal Masses

Context.— Renal malignancies can be divided into cortical- and medullary-based tumors, the latter of which classically infiltrate renal parenchyma by extending between nonneoplastic structures. Although high-grade cortical tumors rarely exhibit same growth pattern, infiltrative morphology should elicit a differential diagnosis to considered in each case. However, these diagnoses challenging distinguish, especially on small biopsy samples. Objective.— To provide an overview clinical, gross, microscopic findings; genetic molecular alterations; immunohistochemical evaluation other tumor types with overlapping morphologies patterns. Data Sources.— Literature review personal observations were used compile information this review. Conclusions.— Collecting duct carcinoma is prototypical tumor, although diagnostic criteria exist, it remains exclusion, ancillary techniques aiding recognition established as well more recently described neoplasms. Other included include medullary carcinoma/renal cell unclassified phenotype, fumarate hydratase–deficient carcinoma, upper tract urothelial carcinoma. Moreover, rare entities excluded, including metastatic lymphoma, melanoma. In addition potential prognostic differences, accurate have important surgical clinical management implications.