A Rare Case of Abdominal IVC Pleomorphic Leiomyosarcoma on 18-F FDG PET CT Scan

Leiomyosarcoma of inferior vena cava (IVC) is a rare malignant tumor, which accounts for 2% of all leiomyosarcoma. Among its multiple histological subtypes, pleomorphic leiomyosarcomas (PLMSs) account for around 8.6%, making it a rare among the rare. We report the rare case of pleomorphic subtype of leiomyosarcoma arising from the IVC where 18-F fluorodeoxyglucose positron emission tomography computed tomography (FDG PET CT) provided help in diagnosing the tumor as well as guide for an optimal site and route for biopsy. 18-F FDG PET CT revealed high grade metabolically active retroperitoneal mass abutting the inferior medial pole of right kidney, IVC, head of pancreas, and duodenum. It also showed thrombus in IVC up to left common iliac vein as well as in right common and bilateral external iliac veins which correlated with the ultrasound Doppler studies. CT-guided biopsy of the retroperitoneal mass showed spindle cell sarcoma, which on further immunohistochemistry were identified to be a pleomorphic subtype of leiomyosarcoma. 18-F FDG PET CT also helped in surgical planning and highlighted the need for adjuvant modalities as PLMS are known to be aggressive tumors with high mortality compared to other leiomyosarcomas.