A Solitary Soft Tissue Mass in the Thigh as the First Manifestation of Occult Lung Squamous Cell Carcinoma: A Case Report

ABSTRACT

A 69‐year‐old male patient developed a painless, gradually increasing mass in the upper part of his right thigh, with no pulmonary symptoms. Magnetic resonance imaging revealed a nodular lesion in the lateral femoral muscle, which was initially suspected to be a primary soft tissue tumour. After the mass was surgically removed, the histopathological examination confirmed squamous cell carcinoma (SCC), and the immunohistochemical staining of P63 and CK5/6 was positive. Subsequent FDG PET/CT examination revealed a hypermetabolic nodule in the upper lobe of the right lung. Endobronchial ultrasound‐guided biopsy confirmed it as primary lung SCC. This case indicates that isolated skeletal muscle metastasis can be the initial manifestation of occult lung cancer. The research results suggest that seemingly isolated soft tissue masses may be the first sign of latent malignant tumours.