Non-small cell lung cancer with a single metastasis, the new stage M1b; does the site matter?

Non-small cell lung cancer (NSCLC) patients with a solitary metastasis are considered to have a more favourable prognosis compared to those with multiple metastases. This is also shown in the 8th tumor, node, metastases edition for lung cancer (TNM8): patients with M1b (single extrapulmonary metastasis) have a superior prognosis than those with M1c disease (multiple metastases). Although not described in the TNM8, site of single metastatic disease may reflect tumour biology and may be of important prognostic value. We report a case of a patient with squamous cell NSCLC and a single skeletal muscle metastasis with a remarkably aggressive disease course.