title: Papillary renal cell carcinoma with oncocytic cells and nonoverlapping low grade nuclei: expanding the morphologic spectrum with emphasis on clinicopathologic, immunohistochemical and molecular features.
abstract: Papillary renal cell carcinoma (PRCC), a morphologically and genetically distinct subtype of RCC, is morphologically separated into 2 subtypes, type 1 and 2, for prognostic purposes. Type 1 PRCC (single layer of small cells, scant pale cytoplasm) is more common and has a favorable prognosis compared with type 2 (pseudostratified high-grade nuclei, abundant eosinophilic/oncocytic cytoplasm). We report the clinicopathologic, immunohistochemical, and molecular data of 7 adult papillary tumors with morphological features distinct from type 1 or 2 PRCC. All tumors demonstrated predominant papillary architecture, lined by cells with oncocytic cytoplasm, and nonoverlapping low Fuhrman grade nuclei (1 or 2). Foamy macrophages were noted in 2 of 7 tumors. No case demonstrated necrosis or psammoma bodies. Most tumors (6/7) were small (mean size, 2.0 cm; range, 0.8-5.7 cm) and limited to the kidney. No tumor recurrence or metastasis was identified (median follow-up, 22 months). All tumors demonstrated trisomy for 7 and 17 by fluorescence in situ hybridization analysis and uniform CK 7, CD10, and alpha-methylacyl-coenzyme A racemase expression, characteristic of PRCC. These results suggest that these tumors are distinct from type 1 (owing to oncocytic cells) and type 2 (owing to low-grade nonstratified nuclei, low stage, and good outcome). Awareness of this favorable spectrum of PRCC is important to avoid its potential misinterpretation as an aggressive type 2 PRCC (owing to oncocytic cells) or rarely as an oncocytoma (owing to oncocytic cells and low-grade nuclei). Morphologic spectrum of these PRCCs emphasizes that the future prognostic model of PRCC may need to be based primarily on the nuclear characteristics, irrespective of the cytoplasmic features.
authors.affiliation: Department of Pathology, University of Michigan School of Medicine, Ann Arbor, MI 48109, USA.
authors.forename: Lakshmi P
authors.initials: LP
authors.lastname: Kunju
authors.forename: Kirk
authors.initials: K
authors.lastname: Wojno
authors.forename: J Stuart
authors.initials: JS
authors.lastname: Wolf
authors.forename: Liang
authors.initials: L
authors.lastname: Cheng
authors.forename: Rajal B
authors.initials: RB
authors.lastname: Shah
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D002292:Carcinoma, Renal Cell / Q000145:classification / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002467:Cell Nucleus / Q000473:pathology; D002869:Chromosome Aberrations; D003593:Cytoplasm / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D007680:Kidney Neoplasms / Q000145:classification / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D014314:Trisomy
chemical_list: D014408:Biomarkers, Tumor