Skeletal muscle metastases from lung cancer

Hematogenous metastases to the limb skeletal muscles are extremely rare. Better understanding of the mechanisms resulting in the relative resistance of skeletal muscle to metastases could have bearing on therapeutic interventions for prevention of metastases. Three patients with non-small cell lung cancer and metastases in the proximal limb muscles are presented. Skeletal muscle metastases may present as painful masses in the proximal skeletal muscles. Subcutaneous and osseous metastases which are more frequent must be excluded by careful physical examination, bone scan and x-rays. Computed tomography (CT) can confirm the location of the tumor within the fascial planes of skeletal muscles and may help in the accurate delineation of the radiation portal. The tumor can be diagnosed and more common causes, such as hematoma or abscess, can be excluded by thin needle aspiration with cytologic examination. Clinical recognition of metastases in this unusual site is important based on our report that total tumor dose of 3600 to 4200 cGy of radiation in fractions of 300 cGy, 5 days a week, is effective in palliation of swelling and pain.