​Updated: 3 August 2005

Patients with metastatic cancer of unknown primary site (primary unknown) have a histological or cytologically documented cancer, but no primary site identified after careful clinical history, full physical examination (including pelvic and rectal exam) and chest radiograph. The management of metastatic cancer when the site of origin of the malignancy is unknown requires a systematic approach.

Metastatic cancer with unknown primary site accounts for 2.5% of referrals to BC Cancer Agency. Incidence rises with age and has no clear-cut predominance by gender. The median survival is about six months and the proportion of patients alive at 1 year is 10-20%. A small proportion (about 5%) are alive at 5 years. Post-mortem examination reveals lung or pancreas primaries in about half of those patients in whom a primary tumour is ultimately identified.

Careful pathological assessment is crucial and specific tumour types should be referred to the appropriate tumour groups (i.e. sarcoma, melanoma). Male patients with midline masses (germ cell cancers) are seen by the Genitourinary Tumour Group. Squamous carcinomas of the  cervical lymph nodes need review by the Head and Neck Tumour Group. However, the majority of tumours are adenocarcinomas or undifferentiated carcinomas.

Triage of patients to Radiation or Medical Oncology will depend on the symptoms needing palliation and the site(s) involved. For example, patients with brain metastases or painful bone metastases are usually treated by a radiation oncologist and patients with liver, lung or soft tissue disease are managed by a medical oncologist. A specific clinic or conference for tumours of unknown primary does not exist at this time, but difficult cases are discussed in a multi-disciplinary fashion by the appropriate specialties.