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Keywords:

  • breast cancer;
  • special type;
  • unfavourable prognosis;
  • HER-2/neu;
  • FISH

Aims:  To investigate whether alterations of the HER2 gene occur more frequently in histologically unfavourable subtypes of invasive breast cancer.

Methods:  The study was composed of nine invasive apocrine, six lipid-rich, 12 glycogen-rich, 11 micropapillary and 33 pleomorphic lobular breast carcinomas. Lymph node involvement was represented in all subgroups. HER2 status was confirmed in all cases by using immunohistochemistry (CB11, Herceptest) and fluorescent in-situ hybridization (FISH) analysis (Vysis).

Results:  Micropapillary and apocrine carcinomas showed the highest rate of protein overexpression (72% and 66%) and gene amplification (45% and 44%). Protein overexpression was common in poorly differentiated pleomorphic lobular carcinomas (56%); however, this subgroup failed to show an increased number of gene copies by FISH (31%). The incidence of HER2 overexpression (33% and 50%, respectively) and gene amplification (25% and 33%, respectively) among glycogen-rich and lipid-rich carcinomas was not higher than that observed in breast cancer generally.

Conclusion:  Our data suggest that preferential involvement of the HER2 gene in micropapillary and apocrine breast carcinomas may contribute to their aggressive behaviour.