INTRODUCTION: HOXB13 is an established prostate cancer susceptibility gene, with germline variants conferring a three- to fivefold increased risk of prostate cancer, frequently with earlier-onset disease. While previous studies have suggested a potential association with colorectal cancer, evidence regarding predisposition to other malignancies than prostate cancer has been inconsistent.
CASE PRESENTATION: We present a case of a 50-year-old male patient with locally advanced gastric adenocarcinoma who was later diagnosed with prostate cancer. Patient's family history was notable for several malignancies, including endometrial carcinoma, thyroid cancer, and breast cancer on the same side of the family. Germline testing was negative for gastric cancer susceptibility genes but identified a germline HOXB13 G84E mutation.
CONCLUSION: To the best of our knowledge, this is the first case report of a patient with a germline HOXB13 variant diagnosed with both gastric and prostate cancer. Moreover, our work highlights the relevance of germline testing in patients with prostate cancer qualifying for genetic counseling.
