title: Unusual fat-containing tumors of the kidney: a diagnostic dilemma.
abstract: Unusual fat-containing renal tumors in a series of 27 cases comprised five categories: atypical and complicated angiomyolipomas (AMLs) (n = 15), including AMLs with extrarenal growth (n = 5), AMLs with undetectable fat (n = 4), and hemorrhagic AMLs (n = 6); fat-containing renal cell carcinomas (RCCs) (n = 9); lipoma (n = 1); liposarcoma (n = 1); and fat-containing renal oncocytoma (n = 1). Fat was present within RCCs by the following mechanisms; lipid-producing necrosis within a large RCC (n = 2), intratumoral bone metaplasia with fatty marrow elements and calcification within a small RCC (n = 2), and entrapment of perirenal (n = 4) or sinus (n = 1) fat by large irregular RCCs. Fat-containing RCC must be considered in cases of fat-containing renal tumors, even though the presence of intratumoral fat is characteristic of AML. A dedicated computed tomography scanning protocol and strict diagnostic criteria are mandatory for accurate diagnosis. Malignancy should be suspected on the basis of the following criteria: presence of intratumoral calcifications; large, irregular tumor invading the perirenal or sinus fat; large necrotic tumor with small foci of fat; and association with nonfatty lymph nodes or venous invasion.
authors.affiliation: Department of Radiology, Necker Hospital, Paris, France.
authors.forename: O
authors.initials: O
authors.lastname: Hélénon
authors.forename: S
authors.initials: S
authors.lastname: Merran
authors.forename: F
authors.initials: F
authors.lastname: Paraf
authors.forename: P
authors.initials: P
authors.lastname: Melki
authors.forename: J M
authors.initials: JM
authors.lastname: Correas
authors.forename: Y
authors.initials: Y
authors.lastname: Chrétien
authors.forename: J F
authors.initials: JF
authors.lastname: Moreau
mesh_terms: D018207:Angiomyolipoma / Q000175:diagnosis*; D002292:Carcinoma, Renal Cell / Q000175:diagnosis*; D003937:Diagnosis, Differential; D003952:Diagnostic Imaging; D005260:Female; D006801:Humans; D007668:Kidney / Q000473:pathology; D007680:Kidney Neoplasms / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged