A case series of Lynch syndrome-associated breast cancer.

432 Background: Studies suggest breast cancer (BC) might be a feature of Lynch syndrome (LS). Further characterization of this risk is required before recommending increased surveillance for BC in LS families. This study describes the prevalence and characteristics of BC amongst LS families in a large familial cancer registry. Methods: The pedigrees of 325 families carrying an MMR gene mutation (149 MSH2 46%, 113 MLH1 35%, 38 MSH6 12%, 19 PMS2 5%, and 6 EPCAM 2%) within the Familial Gastrointestinal Cancer Registry (FGICR) were screened for a diagnosis of BC. The analysis was limited to known or obligate carriers of a MMR gene mutation. The diagnosis and age of diagnosis of BC was confirmed utilizing clinic records and pathology reports where available. Descriptive and Chi-squared statistics were utilized. Results: 39 female mutation carriers from 33 unrelated families with a diagnosis of BC were identified. The average age of BC diagnosis was 53y. The vast majority of families (25/33, 76%) carried MSH2 m...