title: Papillary renal cell carcinoma with low-grade spindle cell foci: a mimic of mucinous tubular and spindle cell carcinoma.
abstract: The solid variant of papillary renal cell carcinoma (PRCC) is distinguishable genetically from mucinous tubular and spindle cell carcinoma (MTSC) of the kidney by the presence of trisomy for chromosomes 7 and 17; however, at the morphologic and immunohistochemical levels, these neoplasms overlap significantly. The key morphologic feature distinguishing these two is thought to be the low grade of the spindle cell areas of MTSC; spindle cell areas in PRCC generally signify sarcomatoid change and are high grade. We report 5 cases of PRCC with low-grade spindle cell foci, closely mimicking MTSC. All patients were male, and ranged in age from 17 to 68 years. All tumors were predominantly solid, featuring compact areas of low-grade spindle cells lining thin, angulated tubules. Mucinous stroma was not appreciated in any case. All cases were diffusely immunoreactive for cytokeratin 7, and focally CD10 positive. All 5 cases showed trisomy of chromosome 7, and 3 of 5 showed trisomy of chromosome 17 by fluorescence in situ hybridization, supporting classification as PRCC. These cases further reported morphologic overlap between MTSC and PRCC. Before a diagnosis of metastatic MTSC or MTSC with unusual morphology is rendered, the possibility of PRCC with low-grade spindle cell foci should be considered. Fluorescence in situ hybridization analysis effectively separates these morphologically very similar yet genetically distinctive entities.
authors.affiliation: Department of Pathology, The Johns Hopkins Medical Institutions, Baltimore, MD 21231-2410, USA. pargani@jhmi.edu
authors.forename: Pedram
authors.initials: P
authors.lastname: Argani
authors.forename: George J
authors.initials: GJ
authors.lastname: Netto
authors.forename: Anil V
authors.initials: AV
authors.lastname: Parwani
mesh_terms: D002288:Adenocarcinoma, Mucinous / Q000235:genetics / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D002277:Carcinoma / Q000235:genetics / Q000473:pathology*; D002292:Carcinoma, Renal Cell / Q000235:genetics / Q000473:pathology*; D002886:Chromosomes, Human, Pair 17 / Q000235:genetics; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D007680:Kidney Neoplasms / Q000235:genetics / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D014314:Trisomy