Cases with HER2 copy numbers of 4 to < 6 (the definition of equivocal HER2 results) were analyzed with alternative Ch17Ps for Smith-Magenis syndrome and retinoic acid receptor α genes.
In all, 171 patients with breast cancer who had HER2 FISH that had increased mean CEP17 copy numbers (> 2.6) were selected for additional chromosome 17 studies that used probes for Smith-Magenis syndrome (SMS), retinoic acid receptor alpha (RARA), and tumor protein p53 (TP53) genes.