WHAT IS ALREADY KNOWN ON THIS TOPIC
Constitutional mosaicism resulting from postzygotic events affecting BRCA1 or BRCA2 is extremely rare.
It can evade conventional germline testing strategies and complicate cancer risk assessment and genetic counselling considerations.
Only 10 cases have been reported in the literature so far.
This study expands the limited spectrum of constitutional BRCA1/BRCA2 mosaicism through detailed molecular and clinical characterisation of the fourth reported case of constitutional mosaicism involving a BRCA2 pathogenic variant.
It also reviews and compares all published cases to date to evaluate diagnostic and management strategies and to inform current clinical practice.
Given the rarity of these events and the absence of dedicated clinical guidelines, this study compares real-world experiences reported in the literature to identify common patterns and areas of consensus in their management.
Moreover, it proposes a practical framework to facilitate a structured and…