Papillary-Predominant FLCN -Mutated Renal Epithelial Neoplasm in Birt-Hogg-Dubé Syndrome.
Ting Zhao, Miranda E Machacek
✦ AI-curated · Sources linked
Case in brief
A 79-year-old woman with Birt-Hogg-Dubé syndrome and a pathogenic germline FLCN frameshift mutation presented with bilateral renal masses and underwent right partial nephrectomy. The kidney-confined 2.5 cm tumor was predominantly papillary, with focal cystic change and rare peripheral nested oncocytic cells. Papillary cores contained oncocytic and clear cells; the tumor also showed nuclear palisading and rare multinucleated cells. Immunohistochemistry was positive for PAX8, AMACR, GPNMB, and cathepsin K, and negative for KIT, KRT7, and CA9, supporting an FLCN-mutated renal epithelial neoplasm with papillary features.
What made this case unusual
Papillary architecture is uncommon in FLCN-mutated renal epithelial neoplasms. The tumor’s papillary-predominant pattern, mixed oncocytic and clear cells, and diffuse weak-to-moderate TFE3 staining could complicate classification.
Diagnostic / clinical pearl
In a patient with Birt-Hogg-Dubé syndrome, papillary morphology does not exclude an FLCN-mutated renal epithelial neoplasm; interpret morphology alongside the clinical history and immunophenotype.