Single-Institute Review of HER-2/Neu-Positive Invasive Lobular Breast Carcinoma in an Arab Population.

BACKGROUND Invasive lobular carcinoma is special subtype of breast cancer that has clinical behavior and morphology distinct from other breast cancer subtypes. It accounts for 5-15% of breast cancer. Overall, HER-2 gene amplification occurs at a significantly lower rate in ILC, but also has been linked to adverse outcomes. Most cases of ILCs with HER-2 overexpression and or amplification generally have the pleomorphic variant. We report the first series of cases from Saudi Arabia for this rare cancer in an Arab population. CASE REPORT Nine patients retrospectively were evaluated with HER-2/neu-positive ILC of the breast that were diagnosed and managed from 2003 to 2020. Four patients were diagnosed as early breast cancer, 3 had metastatic disease and 2 were locally advanced at their initial presentation. The mean age was 58 years; 30% were classic ILC and another 60% were of mixed non-classic variants (histologic pattern represented by nuclear pleomorphism). Management of patients with HER-2-positive ILC was performed according to standard multimodality breast cancer guidelines, consisting of surgery, chemotherapy with anti-HER-2/neu blockade, radiation, and endocrine therapy, based on stage and hormone status. CONCLUSIONS In conclusion, HER-2-positive invasive lobular carcinoma of the breast is uncommon in the Arab population, which has not been previously reported in the literature. Further studies are warranted to explore the biology, molecular characteristics, and clinical course in this group of patients.