Recurrent MED12 exon 2 mutations in benign breast fibroepithelial lesions in adolescents and young adults

Abstract

Aims: Most benign breast fibroepithelial lesions (FEL) in adults harbour recurrent somatic MED12 exon 2 mutations and rare TERT promoter hotspot mutations. We sought to determine the frequency of MED12 exon 2 and TERT promoter hotspot mutations in fibroadenomas (FA) and benign phyllodes tumours (BePT) in adolescents and young adults.

Methods: DNA from 21 consecutive FAs and eight consecutive BePTs in adolescents and young adults was subjected to Sanger sequencing of the exon 2 of MED12 and the TERT promoter hotspot locus.

Results: We identified MED12 exon 2 mutations in 62% and 88% of FAs and BePTs, respectively, and no TERT promoter hotspot mutations. The majority of the MED12 exon 2 mutations identified were in-frame deletions (60%).

Conclusions: As in adults, benign FELs in juvenile patients harbour recurrent MED12 exon 2 mutations.

Keywords: MED12; fibroadenoma; phyllodes tumour; sequencing; telomerase.