A Leiomyosarcoma of Inferior Vena Cava Presenting as a Liver Metastasis Mass in a Patient with History of Transitional Cell Carcinoma Abstract The most probable diagnosis for a newly detected mass in the cancer patients is secondary metastasis. However, the multiple primary tumors should not be off the table of diagnoses. In this study, a 70-year-old man with the history of transitional cell carcinoma (TCC) was reported who had been referred due to a newly detected mass in the hepatic segment one which adhered to the inferior vena cava (IVC). Although the most probable diagnosis according to the patient’s medical history was secondary metastasis, the biopsy revealed a leiomyosarcoma (LMS) tumor. Therefore, a mass biopsy can be determinative for confirming the diagnosis and further management of cancer patients with a newly detected mass.