Genomic testing in carcinoma of unknown primary may have implications for the clinical management of the patient’s current cancer, as well for their family members.

Advice for patients with cancer whose constitutional (germline) genomic testing results are uninformative should be guided not just by their negative result, but also by their personal and family history. The patient and their relatives may still require enhanced cancer screening.

Peutz-Jeghers syndrome is characterised by hamartomatous bowel polyps and mucocutaneous pigmentation, and is associated with an increased risk of a variety of cancers. It is caused by constitutional (germline) pathogenic variants in the serine/threonine kinase 11 (STK11) gene.

Ovarian cancer is the sixth most common cancer among women in the UK, with an estimated 15%–25% caused by heritable germline variants in high-risk cancer predisposition genes.

The identification of a constitutional (germline) BRCA1 or BRCA2 variant in a patient with ovarian cancer has implications for the clinical management of the current cancer and the patient’s future cancer risk; it should also trigger cascade screening in the wider family.

Genomic testing in ovarian cancer affects clinical management of the current cancer and may affect management of the patient’s future cancer risk and that of their relatives.