A young 22-year-old female patient with a known Thymoma, under yearly surveillance, presented with upper respiratory tract infection symptoms. She returned 3 weeks later with an unresolved cough. A chest radiograph demonstrated a retrocardiac homogenous opacity with another opacity obliterating the left cardiac margin. Further, two well-defined homogenous pleural-based opacities in the left upper and lower lung zones were noted. Further evaluation was done with a CT chest and PET scan. CT Thorax confirmed interval invasive features of previously seen left anterior mediastinal mass with direct involvement of pleura, pericardium, and multiple pulmonary nodules denoting invasive malignant thymoma. PET scan reported intensely hypermetabolic left pleural masses likely representing the patient’s thymoma. She underwent a guided tissue biopsy which concluded as Thymoma probably Type B2. She received chemotherapy, radiotherapy, and surgical resection of the lesion with full resolution of the lesion.