Table 2.

Possible opportunities to improve disease-specific understanding of rare breast cancer subtypes.

Opportunity Category	Examples
Clinical Trials	Prospective disease-specific trials
	Basket trials enrolling multiple cohorts, each with a distinct rare tumor (e.g.: DART)
	Retrospective review of outcomes for patients with rare tumors enrolled on completed trials
	Prospective identification of patients with rare tumors for new trials or on-going platform trials
Infrastructure	International collaborations (e.g., International Rare Cancers Initiative)
	Engage cooperative groups (e.g., ETCTN) which enrich for mega-centers where patients with rare breast cancer subtypes often receive care
Technology	Real world data to provide retrospective information or to intentionally follow a cohort of patients with a rare subtype of breast cancer prospectively
	Digital pathology and artificial intelligence to prospectively review and register tumors to reduce issues related to overlapping diagnoses and interobserver variability