title: Topographic molecular profile of pheochromocytomas: role of somatic down-regulation of mismatch repair.
abstract: OBJECTIVE
  Despite extensive molecular investigation of adrenal pheochromocytomas, no information is available on their molecular and mismatch repair (MMR) profiles by topographic compartments.
  
  
  METHODS
  Microdissected samples from the peripheral and internal zones of 143 pheochromocytomas from a referral hospital (95 sporadic and 48 associated with multiple endocrine neoplasia type 2A) were selected for loss of heterozygosity and single nucleotide polymorphism analyses. Five polymorphic DNA regions from TP53, RB1, WT1, and NF1 were systematically studied by PCR-denaturing gradient gel electrophoresis. PATIENTS, OUTCOME MEASURES, AND INTERVENTIONS: Pheochromocytomas were classified as malignant (16 sporadic tumors with distant metastases), locally invasive (30 sporadic tumors showing retroperitoneal infiltration only), and benign (all remaining tumors). Statistical differences were evaluated using Fisher's exact test. MMR was assessed by MLH1/MSH2 sequencing and immunostaining in pheochromocytomas with two or more abnormal microsatellites. No interventions were performed in this study.
  
  
  RESULTS
  Loss of heterozygosity/single nucleotide polymorphism involved TP53 in 40 of 134 informative cases (29.9%), RB1 in 22 of 106 informative cases (20.8%), WT1 in 32 of 120 informative cases (26.7%), and NF1 in 32 of 80 informative cases (40.0%). More genetic abnormalities involving the peripheral compartment were revealed in 34 pheochromocytomas (23.8%): 12 of 16 malignant, 10 of 30 locally invasive, and 12 of 97 benign. Multiple and coexistent genetic abnormalities characterized malignant pheochromocytomas (P < 0.001), whereas locally invasive pheochromocytomas showed a significantly higher incidence of NF1 alterations (P < 0.001). No mutations were identified in MLH1/MSH2, but MMR proteins significantly decreased in peripheral compartments.
  
  
  CONCLUSIONS
  Multiple microsatellite alterations and topographic intratumor heterogeneity characterize malignant pheochromocytomas, suggesting a multistep tumorigenesis through somatic topographic down-regulation of MMR proteins. Locally invasive pheochromocytomas reveal topographic heterogeneity and single-locus microsatellite alterations, especially involving NF1.
authors.affiliation: Department of Pathology, University of Malaga School of Medicine, Malaga E29010, Spain.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Blanes
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Sanchez-Carrillo
authors.forename: Salvador J
authors.initials: SJ
authors.lastname: Diaz-Cano
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000235:genetics* / Q000473:pathology*; D000313:Adrenal Medulla / Q000473:pathology; D020137:Base Pair Mismatch / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D004260:DNA Repair / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics; D004276:DNA, Satellite / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D016158:Genes, p53; D006801:Humans; D019656:Loss of Heterozygosity; D018813:Multiple Endocrine Neoplasia Type 2a / Q000235:genetics; D010673:Pheochromocytoma / Q000235:genetics* / Q000473:pathology*; D020641:Polymorphism, Single Nucleotide; D016160:Retinoblastoma Protein / Q000235:genetics
chemical_list: D017931:DNA Primers; D004273:DNA, Neoplasm; D004276:DNA, Satellite; D016160:Retinoblastoma Protein