title: Frequent alterations of HER2 through mutation, amplification, or overexpression in pleomorphic lobular carcinoma of the breast.
abstract: Mutations in HER2 gene have been identified in a small subset of breast cancer cases. Identification of HER2 mutation has therapeutic implications for breast cancer, but whether a subgroup of breast cancer with a higher frequency of HER2 mutation exists, remains unknown. We analyzed HER2 mutation and pathologic factors on 73 formalin-fixed, paraffin-embedded samples, including 21 pleomorphic invasive lobular carcinoma (p-ILC) cases, 3 pleomorphic lobular carcinoma in situ (p-LCIS) cases, and 49 classic invasive lobular carcinoma (c-ILC) cases. Mutations were identified through direct sequencing. HER2 overexpression and amplification were determined through immunohistochemistry and fluorescent in situ hybridization. Six mutations were identified, including five in the 24 p-ILC or p-LCIS (p-ILC/p-LCIS) cases (20.8 %) and one in the 49 c-ILC cases (2.0 %), and the difference in frequency was significant (p = 0.013). Eight of the 24 (33.3 %) p-ILC/p-LCIS cases exhibited HER2 amplification or overexpression (amplification/overexpression), which was significantly higher than in the c-ILC cases (1/49, 2 %). Mutation and amplification/overexpression were mutually exclusive. HER2 mutations were identified more frequently in the p-ILC/p-LCIS cases with extensive apocrine change (p = 0.018). Combined HER2 alterations through mutation or amplification/overexpression were more frequently identified in p-ILC/p-LCIS cases without estrogen receptor expression. The high frequency (54.1 %, 13/24) of combined HER2 alterations in the p-ILC/p-LCIS cases suggests a crucial role of HER2 in the pathogenesis of p-ILC/p-LCIS. Because of the reported responsiveness of HER2 mutation to anti-HER2 therapy, p-ILC patients without HER2 amplification/overexpression should receive HER2 mutation analysis to identify this therapeutically relevant target.
authors.affiliation: Department of Pathology, College of Medicine, National Taiwan University Hospital, No. 1 Jen-Ai Road, 1st Section, Taipei, 100, Taiwan.
authors.forename: Huang-Chun
authors.initials: HC
authors.lastname: Lien
authors.forename: Yu-Ling
authors.initials: YL
authors.lastname: Chen
authors.forename: Yu-Lin
authors.initials: YL
authors.lastname: Juang
authors.forename: Yung-Ming
authors.initials: YM
authors.lastname: Jeng
mesh_terms: D001483:Base Sequence; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D018275:Carcinoma, Lobular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004252:DNA Mutational Analysis; D005260:Female; D005784:Gene Amplification; D015870:Gene Expression; D005787:Gene Frequency; D006801:Humans; D009154:Mutation; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics*
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human