Metastasis (mets) of unknown primary origin

Most patients with newly diagnosed cancer are found to have a clearly defined primary tumour after initial investigation and staging. In England and Wales about 4% of these patients are found to have cancer without an identifiable primary site, despite exhaustive tests

Most patients who have malignancy without an identifiable primary site have tumours derived from epithelial cells, that is, carcinoma of unknown primary origin.

Current standard evaluation of cancer of unknown primary requires histopathologic evaluation and identification of favorable risk subtypes that can be more definitively treated or have superior outcomes (2)

• current standard treatment of the unfavorable risk subtype requires assessment of prognosis and consideration of empiric chemotherapy
• the expanding use of next generation sequencing in advanced cancers (use of molecular tissue of origin tests) offers the potential to identify a subgroup of patients who have actionable genomic aberrations and may allow for further personalization of therapy

Reference:

• 1) NICE (April 2023). Metastatic malignant disease of unknown primary origin - Diagnosis and management of metastatic malignant disease of unknown primary origin
• 2) Lee MS, Sanoff HK. Cancer of Unknown Primary. BMJ 2020;371:m4050