A woman in her 60s presented to her local physician with a spontaneous onset of pain and swelling on the medial side of her right thigh. D-dimer and C-reactive protein (CRP) levels were tested and found to be increased, and she was then referred to our hospital’s cardiology department. A lower extremity venous ultrasonography was performed and thrombi were observed in the popliteal, peroneal, posterior tibial, and soleal veins in the right leg. The right great saphenous vein was also found to have a thrombus up to the confluence of the femoral vein. Suspecting more extensive thrombi, an examination of the abdominal region was performed, and a large tumor was discovered in the pelvis. The tumor had a mixed pattern on ultrasound, with a predominantly solid body and was suspected to be malignant and of ovarian origin. She was started on anticoagulation with rivaroxaban in the Department of Cardiology, after which she was referred to a gynecologist. During a thorough examination in the Department of Gynecology, multiple cerebral infarctions occurred and were treated immediately with intravenous heparin. Ovarian cancer stage I was suspected on Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) of the pelvic region. She was taken to surgery with complete resection of the tumor and surgical staging and a final diagnosis of ovarian clear cell carcinoma stage IC3. Multiple cerebral infarctions and prior deep vein thrombosis were also diagnosed and were attributed to Trousseau’s syndrome. While it is well-known that malignancies increase thrombogenesis, it is still rare for a malignancy to be detected at the onset of deep vein thrombosis. This case report is of a Stage IC3 ovarian cancer detected during evaluation of suspected Trousseau’s syndrome, during ultrasound evaluation of the lower extremity and further defined as potentially malignant pre-operatively during cross sectional scanning.