Clinical challenges and proposed solutions for patients with invasive lobular breast cancer

Background: Invasive lobular carcinoma (ILC) is the second most common type of breast cancer and is increasingly recognized as a separate entity from invasive breast cancer of no-special type. Here, we present the current standings and challenges of clinical ILC research and discuss possible solutions to address these challenges. Design: European and United States experts on ILC have summarized the recent developments, ongoing endeavors and remaining challenges concerning the histopathological diagnosis, imaging and treatment of ILC. Results: Recent endeavors have led to guidelines for a more uniform and standardized pathological diagnosis of ILC. Future efforts are needed to refine the histological and biological subclassification and determine the indications for use of artificial intelligence for pathological diagnosis. Since standard-of-care imaging tools are suboptimal for ILC screening and local and systemic staging, new modalities such as contrast-enhanced mammography, novel positron emission tomography tracers and diffusion-weighted magnetic resonance imaging are under investigation. An alternative to the currently used RECIST v1.1 criteria is needed for clinical trial response assessment, as it is not uniformly applicable for patients with metastatic ILC. The use of liquid biopsies for detecting disease progression needs dedicated research. Regarding treatment, the efficacy of novel breast cancer therapies needs to be examined specifically for ILC, and evaluation of drugs targeting ILC-specific or enriched targets is warranted. Conclusions: While great progress has been made in ILC research, many challenges remain and require further investigation in the clinic to optimize treatment and outcomes for those diagnosed with this common tumor type.