Synchronous small bowel and atypical primary leiomyosarcoma of inferior vena cava in a patient with RB1 mutation

A 72-year-old Caucasian man presenting with non-specific upper abdominal pain had asymmetric soft tissue thickening of the small bowel wall on computed tomography (CT), which was pathologically proven to be leiomyosarcoma (LMS). At the same time point patient had incidentally but retrospectively detected lesion in IVC on CT scan which was subsequently imaged with PET/CT and MRI and was histologically proven to be also LMS. We present clinical and imaging features along with pedigree of this unique case of synchronous primary LMS involving the small bowel and inferior vena cava in a patient with RB1 gene mutation and a significant family history of multiple malignancies. To our knowledge, the synchronous primary LMS at two different sites has not been described. Clinicians and radiologists should keep in mind the possibility of a synchronous primary LMS in patients with genetic predisposition before making the diagnosis of a metastatic lesion or other malignancy as localized primary tumors remain potentially curable, whereas metastatic sarcoma is most often incurable.