A signal for signet.

While most lobular breast cancers are treated easily enough, the diagnosis often prompts a genetic panel which can then reveal a germline CDH1 pathogenic variant. This mutation probably makes you think of gastric cancer, and indeed over 30-40% of carriers eventually develop gastric cancer. But even more, over 40-50%, develop lobular breast cancer—granted these carriers only make up a tiny fraction of all lobular breast cancers. This prospective study of known carriers of a CDH1 pathogenic variant inquired if having only a family history of lobular breast, and not gastric, cancer impacted risk of harboring an occult notorious signet ring cell gastric adenocarcinoma. The answer was a resounding no. Of 16 patients with a lobular breast cancer who were found to have a CDH1 mutation and elected for prophylactic gastrectomy (at a median age of only 50 years), 15 (94%) had an occult signet ring cell adeno on final pathology. | Gamble, JAMA Surg 2021