Desmoid tumor with ossification in chest wall: possible involvement of BAMBI promoter hypermethylation in metaplastic bone formation.
A rare case of desmoid-type fibromatosis with focal metaplastic bone in the chest wall suggested that enhanced responsiveness to BMP signaling by decreasing BAMBI expression through promoter hypermethylation plays a crucial role in the formation of metaplastic bone.


BACKGROUND
Desmoid-type fibromatosis, originating from mesenchymal cells with myofibroblastic features, is a locally aggressive and frequently recurring infiltrative lesion. One such sporadic case with metaplastic ossification in the chest wall is presented.


METHODS
A 43-year-old man was referred to the hospital with a gradually enlarging hard mass in the left anterolateral chest wall. A thoracotomy was carried out, and histopathological specimens were used for immunohistochemical, genetic, and methylation studies.


RESULTS
Accumulation of altered beta-catenin associated with a somatic heterozygous activating mutation in codon 41 was detected in the typical desmoid-type fibromatosis and at the ossifying focus. Among factors related to bone formation and the classical wnt-beta-catenin signaling pathway, BMP and activin membrane-bound inhibitor (BAMBI) expression was specifically downregulated at the ossifying focus. Hypermethylation of the BAMBI promoter was observed in microdissected tissue from the ossifying focus but not in that from the typical desmoid-type fibromatosis.


CONCLUSIONS
Because both BMP and classical Wnt/beta-catenin/LEF1 signaling cooperatively and mutually induce differentiation of mesenchymal cells into osteoblastic cells and promote bone formation, the epigenetic event leading to the enhanced responsiveness to BMP signaling may play a crucial role in the formation of metaplastic bone.
Kitazawa
Sohei
S
Division of Molecular Pathology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Japan. kitazawa@med.kobe-u.ac.jp
Kitazawa
Riko
R
Obayashi
Chiho
C
Yamamoto
Tetsuji
T
D000328:Adult; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000032:analysis / Q000378:metabolism; D019175:DNA Methylation; D015536:Down-Regulation; D044127:Epigenesis, Genetic; D018222:Desmoid Tumors / Q000276:immunology / Q000473:pathology*; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009999:Ossification, Heterotopic / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D011401:Promoter Regions, Genetic; D035441:Thoracic Wall / Q000473:pathology; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000378:metabolism
C485671:BAMBI protein, human; C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D008565:Membrane Proteins; D016212:Transforming Growth Factor beta