title: Renal Splenosis: Renal Mass Biopsy Diagnosis of a Tumor Clinically Mimicking Renal Cell Carcinoma.
abstract: Renal mass biopsy is increasingly used to guide conservative tumor management, placing increasing importance on pathologists' ability to diagnose small tumor samples. A 66-year-old man with a history of prior splenectomy for trauma presented for urologic evaluation after identification of a left 5.8 cm renal mass. Partial envelopment of the mass by renal parenchyma and equivocal enhancement on computed tomography raised concern for renal cell carcinoma. Needle-core biopsy revealed blood, subtle vasculature, few aggregates of lymphocytes, and rare renal tubules. Immunohistochemical staining revealed CD8-positive sinusoids but negative reactivity for epithelial antigens (PAX8, keratin, epithelial membrane antigen, carbonic anhydrase IX), supporting diagnosis of renal splenosis. Renal splenosis is a rare phenomenon that can form a sizeable intrarenal mass, mimicking renal cell carcinoma. Pathologists' awareness of this uncommon occurrence may avoid unnecessary surgery. CD8-positive sinusoids and negative epithelial markers are helpful confirmatory features in the biopsy setting.
authors.affiliation: *Department of Pathology and Laboratory Medicine †Josephine Ford Cancer Institute, Henry Ford Health System ‡Wayne State University School of Medicine, Detroit, MI.
authors.forename: Sean R
authors.initials: SR
authors.lastname: Williamson
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D001707:Biopsy, Needle; D016827:CD8 Antigens / Q000378:metabolism; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000473:pathology; D003937:Diagnosis, Differential; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007668:Kidney / Q000473:pathology*; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D017890:Splenosis / Q000175:diagnosis* / Q000473:pathology
chemical_list: D015415:Biomarkers; D016827:CD8 Antigens