A Portrait of HER2- Low Invasive Lobular Carcinoma (ILC) of Breast. Lounes Djerroudi Anne Vincent-Salomon

Our host discusses with Drs. Djerroudi and Vincent-Salomon, from the Institut Curie in Paris France, their recent study comparing HER2-negative invasive breast cancer of no special type (IBC-NST), with HER2-negative ILC. HER2-negative ILC had a higher frequency of HER2-zero cases (59.4% vs 53.7%) and a lower frequency of HER2-low (40.6% vs 46.3%). Clinicopathological features associated with HER2-low status (vs HER2-zero) in ILC were older age, postmenopausal status, non-classic ILC histological types, higher grade, and ER expression. While HER2-low ILC patients had a lower risk of local recurrence (vs HER2-zero) there was no association between HER2 status and either breast cancer specific survival or distant metastasis-free interval. ERBB3 was the unique mutated gene exclusively associated with HER2-low ILCs, albeit mutated at a low frequency (7.1%). The guests highlighted the potential therapeutic significance of their findings that HER2-low ILCs exhibit unique molecular and clinical attributes.