A Patient with Squamous Cell Carcinoma of the Lung Selectively Developing Multiple Metastases in Skeletal Muscle

Metastases to skeletal muscle are extremely rare. A 42-year-old male with squamous cell carcinoma of the lung who selectively developed metastases to skeletal muscle is reported. The patient was hospitalized in August 1988. Chest X-ray examination revealed a mass in the right middle lobe associated with unilateral hilar lymphadenopathy and malignant pleural effusion. Staging procedures, including CT of the brain, CT of the abdomen, and radionuclide bone scan disclosed negative extrathoracic metastases. A partial regression of the mass and the complete disappearance of the pleural effusion for 7 weeks duration were achieved with chemotherapy regimen of cisplatin and vindesine. Following the relapse of the primary lesion, multiple severely painful nodules developed on his back, right forearm, and left thigh in February 1989 despite continuing chemotherapy. These nodules were shown to be intramuscular masses by MRI and proved to be metastases by percutaneous needle aspiration cytology. Restaging procedures again disclosed no extrathoracic metastases except those in skeletal muscle. The patient died of progressive primary lesion and intractable hypercalcemia in July 1989. Postmortem examination was not done. Accordingly, it was uncertain whether the metastatic disease was confined to the skeletal muscle, however, the patient was of interest because of the fact that the skeletal metastases were clearly detectable by MRI and by clinical means, and those were the only extrathoracic manifestations until his death.