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Kidney tumor - cysts, children, adult benign

Benign (usually) adult tumors


Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 18 April 2012, last major update February 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.


● Benign tumor of uniform round / polygonal cells with abundant, intensely eosinophilic and granular cytoplasm with uniform small, round and central nuclei with evenly dispersed chromatin

Panels of markers to differentiate renal tumor subtypes:
● Beta defensin1+, parvalbumin+ and vimentin- in 100% (8/8) (small series, Am J Surg Pathol 2003;27:199)
● Vimentin- (may be focally positive), GSTalpha- and EpCAM- (may be focally positive, Arch Pathol Lab Med 2007;131:1290)
● Second line markers are CD117+, CK7-


● 4-7% of adult renal epithelial tumors
● Adults age 50+; 2/3 men; usually incidental
● May co-exist with renal cell carcinoma
● Rarely associated with renal failure due to multiple tumors or large bilateral tumors (Arch Pathol Lab Med 2002;126:648)


● Arises from intercalated cells of collecting duct

Clinical features

Birt-Hogg-Dube’ syndrome:
● Rare, autosomal dominant syndrome of small dome-shaped papular fibrofolliculomas of face, neck and upper trunk
● Associated with multiple renal tumors (mean 5.3), usually chromophobe carcinomas or oncocytomas, oncocytosis, pulmonary cysts and spontaneous pneumothorax (Am J Surg Pathol 2002;26:1542)
● Associated with 17p12q11 abnormality involving folliculin protein (Arch Pathol Lab Med 2006;130:1865)

Radiologic images

CT shows circumscribed and homogeneous tumor except for an irregular central zone which proved to be a central scar

MR shows same tumor with prominent central scar

Case reports

● 56 year old man with bilateral renal oncocytosis (Arch Pathol Lab Med 2004;128:e177)
● 62 year old man (Arch Pathol Lab Med 2003;127:1229)
● 61 year old man with ectopic and crossed fused kidneys (Arch Pathol Lab Med 2002;126:648)
● 67 year old man with multilocular cystic tumor (J Clin Pathol 2006;59:223)
● With clear cell carcinoma (Am J Surg Pathol 1998;22:271)
● With focal chromophobe carcinoma and metastasis (Int J Surg Pathol 2009;17:158)
● Encased within fibrotic shell resembling retroperitoneal fibrosis (Arch Pathol Lab Med 1994;118:1026)


● Benign behavior if follow strict diagnostic criteria, even if degenerative atypia (Am J Surg Pathol 1997;21:871)
● Excision is curative

Clinical images

Giant (20 cm) tumor in pregnant womanr

Gross description

● Well circumscribed, unencapsulated, solid, homogenous, mahogany or brown-yellow (same as cortex), 3-6 cm, stellate central scar in larger lesions
● 5% are bilateral or multifocal; may invade renal capsule or renal vein
● 20% have gross hemorrhage but necrosis is rare
● Gross appearance is an important criteria

Gross images

Mahogany brown tumor has stellate central scar

Left to right: stellate scarred zones; central cystic change, well circumscribed tumor

Stellate central scar #1, #2

Well circumscribed #1, #2

Light brown tumor with central scar #1, #2

Micro description

● Nesting, alveolar or tubular patterns (closely packed at periphery, more separated centrally) of uniform round / polygonal cells with abundant, intensely eosinophilic and granular cytoplasm, uniform small, round and central nuclei with evenly dispersed chromatin and smooth contour of nuclear membrane, occasional degenerative atypia (bizarre nuclear pleomorphism), focal vacuoles possible near areas of fibrosis
● Stroma is myxoid or hyalinized
● Occasionally cystic change, psammoma bodies, variably sized tubular structures, capsular / perinephric fat invasion (20%), vascular invasion (5%)
● Oncoblasts: small cells with minimal cytoplasm and dense hyperchromatic nuclei
● No papillary pattern (although may have small papillary fronds in areas of cystic change), no clear / spindle cells, no necrosis, no perinuclear halo
● If mitotic figures in more than one 20x field, classify as eosinophilic chromophobe carcinoma
● Grossly noted scar is composed of central loose stroma surrounded by closely packed nests of cells
● Nuclear grading not necessary since benign behavior (Am J Surg Pathol 1997;21:1)

Micro images

Sheets of cells with abundant eosinophilic cytoplasm

Cells have granular acidophilic cytoplasm and small, round and regular nuclei slightly less than 10 um

Scarred zone has tumor cells separated by mature hyalinized fibrous connective tissue

Incompletely differentiated oncocytes

Alveolar nests

Alveolar nests of cells with loose myxoid stroma

Cording (left) and trabecular (right) patterns

Tubulocystic pattern

Osseous metaplasia

Invasion of periphephric fat

Multicystic tumour with thickened septa

Focal degenerative atypia

Birt-Hogg-Dubé associated tumors

62 year old man - figures 1/2: nests of round to polygonal cells with abundant granular, eosinophilic cytoplasm and central round / oval nuclei; fig 3: EM shows abundant abnormal mitochondria with parallel cristae

Bilateral renal oncocytosis with renal failure


Comparison with classic and eosinophilic variant of chromophobe carcinoma: H&E and Hale’s colloidal iron

Vimentin staining

Parvalbumin staining: figure G-positive (unusual); fig H-negative

Bottom: EpCAM- (only focally positive) versus diffusely positive in chromophobe renal cell carcinoma (top)

Cytology description

● Large cells with homogenous granular cytoplasm, nuclei have no / mild nuclear membrane irregularities, tiny nucleoli, mild pleomorphism and only an occasional large, more hyperchromatic nucleus (Cancer 1999;87:161)

Cytology images

Abundant granular cytoplasm and small, round and very regular nuclei

Small clusters and single cells with uniform cytoplasm

Diff-Quik shows homogeneous granular cytoplasm and round, regular nuclei without grooves

Positive stains

● Low molecular weight cytokeratin (CK 8/18, may be dot like)
● CK14 (strong)
● Vimentin (focally positive in 73%, usually at edge of central scar or in small clusters scattered throughout the tumor, Arch Pathol Lab Med 2007;131:1782)
● Also parvalbumin (calcium binding protein, Mod Pathol 2001;14:760), RON proto-oncogene (also in chromophobe renal cell carcinoma, Am J Surg Pathol 2004;28:1045), CD117 / c-kit (Am J Surg Pathol 2004;28:676)
● E-cadherin, S100 (Hum Pathol 2006;37:462), kidney-specific cadherin (Am J Clin Pathol 2006;126:79)

Negative stains

● Hale’s colloidal iron (may be positive at luminal surface in tubular areas)
● CK7 (may have intensely positive scattered cells in a background of negative staining cells), CK20 (variable)
● Sudan fat stain
● RCC-MA (Am J Surg Pathol 2001;25:1485), N-cadherin, CD10 (usually)
● Low Ki-67 labeling index (Mod Pathol 1998;11:1115)

Electron microscopy description

● Marked increase in mitochondria, predominantly uniform and round with stacked parallel (lamellar) cristae, which causes the eosinophilia
● Few microvesicles in the apical portion of the cytoplasm with rare, short and stubby microvilli
● No / rare other organelles, lipid, glycogen, microvilli or brush border (Am J Surg Pathol 2000;24:1247)

Electron microcopy images

Cytoplasm is packed with large mitochondria

Molecular description

● Chromosome 1 abnormalities in 88% of bilateral tumors versus 28% of single tumors (Arch Pathol Lab Med 2007;131:81, Am J Clin Pathol 2008;129:377)
● mt-DNA mutations are common (Hum Mol Genet 2008;17:986)

FISH images

Normal chromosome numbers for #2 and #10 by FISH


Loss of chromosomes 1 (left), 1 and 17 (right)

Differential diagnosis

Chromophobe carcinoma, eosinophilic variant: diffuse, solid growth but no nesting pattern; has distinct, thickened cell border; wrinkled nuclei with binucleation, perinuclear halos, mitotic figures, diffusely and strongly positive for Hale’s colloidal iron, microvesicles by EM, abnromalities by interphase FISH (Am J Clin Pathol 2010;133:116)
Clear cell carcinoma with granular cytoplasm: compact alveolar growth pattern; also hemorrhage, necrosis and frequent mitotic figures, long microvilli by EM, 3p-

End of Kidney tumor - cysts, children, adult benign > Benign (usually) adult tumors > Oncocytoma

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