pecomas
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PURE EPITHELIOID PECOMAS (SO-CALLED EPITHELIOIDANGIOMYOLIPOMA) OF THE KIDNEY: A CLINICOPATHOLOGICSTUDY OF 41 CASES: DETAILED ASSESSMENT OF MORPHOLOGYAND RISK STRATIFICATION
Nalan Nese et al AJSP Feb 2011
INTRODUCTION PEC
Prototype cell of PEComasUnique morphological, IHC, ultrastructural, genetic
featuresUnknown normal histologic counterpart
Histogenetically linked tumoursRenal & hepatic angiomyolipomas (AML)Clear cell sugar tumour of the lungPulmonary lymphangioleiomyomatosisClear cell myomelanocytic tumour of ligamentum
teres
Phenotypically – Smooth m, epithelioid, lipid-rich
IHC - Myogenic markers (spindle ) - Melanocytic markers (epithelioid )
WHO – A mesenchymal tumour composed of histologically & IHC distinctive PECs
Strong association b/w PEComas and TSC AD genetic diseaseLosses of TSC1(9q34) & TSC2 (16p13.3)
Kidney PEComas – related to triphasic typical AML
Unknown aspectsInclusionary and definitional criteria with
variable percentage of epithelioid cells required to make the diagnosis
Clinicopathologic parameters that predict malignant outcome
AIM – To investigate the clinicopathologic
parameters of a large series of well characterized pure renal PEComas using consistent definitional study criteria to potentially assist in risk stratification or progression of patients with these tumors
MATERIALS AND METHODS 41 cases from multiple institutions
Composed of purely epithelioid cells, adipocytic component < 1 – 2%“ Pure ” – separate these cases from those which
have variable epithelioid component
IHC-ve for CK, CAM5.2, EMA+ve for 1/more melanocytic and myogenic
marker
C/FsAge, Sex+/- TSCPresence of mets at time of diagnosisFollow –up information
Local recurrenceRegional lymph node involvementDistant metsTime to mets and recurrenceSites of metsPatient status at last follow up
Pathologic featuresConcurrent small AMLsTumor sizeStatus of confinement to kidneyInvolvement of renal vein
HPEMorphologic architectural patternMitotic count/50hpfNecrosisDegree of nuclear atypiaPresence of multinucleate giant cells
RESULTSAge – 14 – 69 years, mean – 40.7Even sex distributionSize – 2 – 37cm, mean – 11.9 cmGrossly
HPEPEComa with carcinoma like growth
(Pattern A) – 20 cases
PEComa with epithelioid & plump spindled cells in diffuse growth (Pattern B) – 15 cases
PEComa with combined Ca-like & diffuse growth pattern – 5 cases
PEComa with Ca like growth (Pattern A)
PEComa with pattern B
Giant cells
PEComa with mixed pattern
9/30(30%)
13/31(41.9%)
10/31(32.2%)
5/2917.2%
48.5%
10/3033%
30%
STATISTICAL ANALYSIS & RISK STRATIFICATION
DISCUSSION Pure epithelioid PEComa of kidney is a
malignant tumour
Malignant potential with % of epithelioid component
Nomenclature systemTriphasic/typical histologically classic AMLPure epithelioid PEComa - >95% epithelioid
histologyAML with components of epithelioid PEComa
histology of < 95% - specify % of epithelioid areas
Need for accurate diagnosisMalignant behaviourTargeted therapy - Sirolimus
D/DsClear cell RCCChromophobe RCCOncocytomaRCC with sarcomatoid
transformationMets from malignant melanoma
ApproachUnusual renal epithelial -appearing
Age < 50 years
Occ focal microscopic areas of adipocytic diff
Ca-like growth, epithelioid & plump spindled cells & diffuse growth, discohesive sheets of ganglion-like cells, interstitial hemorrhage, and numerous giant cells
IHC - -ve epithelial markers, +ve myogenic & melanocytic markers
Pure epithelioid PEComas have significant overlap in morphology with more commonly occurring neoplasms in the kidney, such as clear cell RCC.
Once the appropriate diagnosis of pure epithelioid PEComa is made by appropriate IHC support, these potentially malignant tumours may be stratified into low, intermediate, and high risk for progression categories based on the documentation of clinicopathologic parameters
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