Lung squamous cell carcinoma with brachial soft tissue metastasis responsive to gefitinib: Report of a rare case

Metastasis of lung cancer to soft tissue is rare and patient outcomes are generally poor. There are no reports describing soft tissue metastasis in lung squamous cell carcinoma (SCC), in which gefitinib treatment was effective not only for the primary tumor but also the metastatic lesion. A 61‐year‐old Asian woman presented to our facility with pain and a mass in the brachium. An additional tumor was identified in the lung. As we suspected soft tissue metastasis of lung cancer, an incisional biopsy was performed, yielding a diagnosis of SCC. The brachial tumor continued to grow and became exposed at the biopsy site when the incisional wound dehisced. Because the biopsied specimen was positive for an epidermal growth factor receptor (EGFR) gene mutation, we commenced gefitinib administration. This treatment resulted in the rapid shrinkage of both the brachial metastasis and the primary tumor, followed by healing of the wound. Therefore, tyrosine kinase inhibitors should be used for cases that present EGFR activating mutations independently from the presence of skin and soft tissue metastases.