[Favourable course of cancer of unknown primary]

Favourable course of cancer of unknown primary Background Most patients with cancer of unknown primary have a very poor prognosis. Case description A 61-year-old woman was diagnosed with a cancer of unknown primary that had metastasised to the lymph nodes in the right axilla and the peritoneum. Because she could not be allocated to a treatable sub-group, she was eligible for treatment as part of a clinical trial. Prior to commencing treatment, molecular testing was conducted, the result of which suggested the primary tumour was a melanoma. We subsequently treated the patient with ipilimumab. Four years after diagnosis, there is no evidence of active disease and the patient remains in an excellent state of health. Conclusion Molecular and genetic testing can improve diagnosis and treatment options in patients with CUP. In the near future, PET-CT diagnostics and whole genome sequencing will probably suffice to identify the primary tumour.