A 45 year-old woman complaining of breast pain was diagnosed with having HER2-positive breast cancer. The patient underwent lumpectomy followed by a period of chemotherapy including adjuvant treatment. Over the course of their treatment, the patient developed a urinary tract infection that required antimicrobial therapy, which initially consisted of atrimethoprim / sulfametoxazole combination drug. However, the patient during the course of her therapy suffered multiple recurrent infections and was, consequently, enrolled in a clinical trial to test the efficacy of a new mannoside anti-infective agent. Question: With reference to signaling pathways, discuss the pathogenesis of HER2-positive breast cancer. In your answer, include discussion on the differential diagnosis of this condition.
Approximately 25% of breast cancer cases, the cancer cells have an excess of the HER2 protein. This is caused by a mutation in the HER2 -human epidermal growth factor receptor 2 gene. When mutation of HER2 gene occurs, it causes cells in the breast to grow and divide at an uncontrolled pace, resulting to growth of a tumor.
Diagnosis of HER2-positive breast cancer: