BRCA1 hereditary cancer (four-generation)

Scenario

A genetic counselor documents a four-generation BRCA1 pedigree for a patient referred after a personal diagnosis of breast cancer at age 35. The NSGC-standard pedigree distinguishes affected, carrier, and presymptomatic individuals — critical for insurance pre-authorization and cascade testing recommendations for at-risk relatives.

Annotation key

• affected — full fill; individual has been diagnosed with the condition
• carrier — half fill; individual carries the mutation but is currently asymptomatic
• presymptomatic — quarter fill or dot; positive genetic test but no clinical diagnosis yet
• proband — triangle marker; the individual who triggered clinical investigation
• deceased — diagonal slash through the symbol

How to read

The pattern of affected females across three generations (I-2, II-1, III-1) is the red flag for hereditary BRCA1. The proband (III-1) is the entry point. Her aunt (II-3) is a carrier who has already passed the mutation to III-6. The presymptomatic sibling (III-3) has tested positive but is not yet diagnosed — she receives enhanced surveillance recommendations.