Hereditary Leiomyomatosis and Renal Cell Carcinoma Syndrome (HLRCC): A Contemporary Review and Practical Discussion of the Differential Diagnosis for HLRCC-Associated Renal Cell Carcinoma.

CONTEXT.—: Hereditary leiomyomatosis and renal cell carcinoma syndrome (HLRCC) is an uncommon disorder with germline-inactivating mutations in the fumarate hydratase ( FH) gene. The kidney cancers that develop in patients with HLRCC are often unilateral and solitary, with a potentially aggressive clinical course; morphologic identification of suspicious cases is of the utmost importance. OBJECTIVE.—: To review classic morphologic features of HLRCC-associated renal cell carcinoma, the reported morphologic spectrum of these tumors and their mimics, and the evidence for use of immunohistochemistry and molecular testing in diagnosis of these tumors. DATA SOURCES.—: University of Michigan cases and review of pertinent literature about HLRCC and the morphologic spectrum of HLRCC-associated renal cell carcinoma. CONCLUSIONS.—: Histologic features, such as prominent nucleoli with perinucleolar halos and multiple architectural patterns within one tumor, are suggestive of HLRCC-associated renal cell carcinoma. However, the morphologic spectrum is broad. Appropriate use of FH immunohistochemistry and referral to genetic counseling is important for detection of this syndrome.