Detection of β-catenin mutations in paraffin-embedded sporadic desmoid-type fibromatosis by mutation-specific restriction enzyme digestion (MSRED):: An ancillary diagnostic tool

Desmoid-type fibromatosis is a locally aggressive deep soft tissue tumor. Some cases are associated with adenosis polyposis coli germline mutations whereas others harbor somatic P-catenin point mutations mainly in exon 3, codons 41 and 45. These mutations result in stabilization of P-catenin, and activation of the Writ signaling pathway. The aim of this study was to determine the specificity and sensitivity of these 3 most common P-catenin mutations in the diagnosis of desmoid-type fibromatosis using paraffin-embedded material. The results were compared with nuclear expression of P-catenin. Mutation-specific restriction enzyme digestion methodology was employed to detect the 3 mutations. One hundred and thirty-three cases were analyzed, including 76 desinoid-type, and 18 superficial fibromatosis, in addition to a further 39 fibromatosis mimics. A restriction site was present for analysis of the codon 41 mutation. Mismatch primers were designed for the codon 45 mutations. Mutations were detected in 66 cases (87%) of 76 desmoid-type fibromatosis (71 extra-abdominal). Of these, 34 (45%) were in codon 45 (TCT > TTT), 27 (35%) in codon 41 (ACC > GCC), and 5 (7%) in codon 45 (TCT > CCT). No mutations were detected in the other lesions studied. All desmoid-type fibromatosis cases and 72% of the mimics tested