Incidental Detection of Clinically Silent Myocardial Metastasis from Lower Limb Cutaneous Squamous Cell Carcinoma on [18F]FDG PET/CT

Myocardial metastasis from cutaneous squamous cell carcinoma (cSCC) is extremely rare and often clinically silent. We describe a 32-year-old man with recurrent invasive cSCC of the right lower limb who underwent contrast-enhanced [ 18 F]-fluorodeoxyglucose positron emission tomography/computed tomography [ 18 F]FDG PET/CT for systemic staging after multiple surgical resections and a hindquarter amputation. PET/CT showed intensely hypermetabolic lesions in the right inguinal region, left groin and lower abdominal wall, indicating active metastatic disease. Additionally, a focal hypermetabolic lesion (SUVmax 10.05), clearly exceeding physiological myocardial uptake, was found in the right ventricular apex with extension into the interventricular septum, suggesting myocardial metastasis. Transthoracic echocardiography later confirmed a corresponding intracardiac mass with preserved ventricular function. The patient was asymptomatic from a cardiac perspective. The detection of myocardial involvement resulted in disease upstaging and the start of systemic palliative therapy. This case emphasizes the importance of whole-body [ 18 F]FDG PET/CT in uncovering rare and clinically hidden metastatic site that can significantly influence staging and treatment planning.