e19645 Background: The natural history of isolated gonadal vein thrombosis (GVT) occurring in cancer patients (pts) is not well described in the medical literature. GVT in cancer pts it is of uncertain clinical significance. Methods: Utilizing a software program allowing a searchable database of radiology reports, the computerized tomographic scan (CT) reports of pts at a single cancer center from January 1, 2004 to June 30, 2011, were searched for the term “gonadal vein thrombus”. Pts included in this analysis had a diagnosis of cancer, isolated GVT (i.e. no evidence of thrombosis at another site), and at least six months of follow-up information. Results: 162 cancer pts with GVT were identified for analysis [median age 57.8 ± 12 years, right GVT 89 pts (54.9%), left GVT 59 pts (36.4%), bilateral 14 pts (8.6%)]; the majority of the pts (96, 59.3%) had a non-gynecologic malignancy. At the time of diagnosis of GVT the majority of pts were receiving chemotherapy (84, 51.9%); 70 pts (43.2%) had surgery within the prior six months (the most common being hysterectomy, 127 pts, 78.6%). The majority of pts in this study had metastatic disease (93, 57.4%) as well as active cancer (138, 85.1%, defined as GVT occurring at the time of cancer diagnosis, disease recurrence, metastatic disease, or treatment for cancer within the prior six months); median follow-up time was 22 months. A minority of pts received anticoagulation (28pts, 17.2%). Twenty-two pts (13.6%) developed a recurrent venous thromboembolic event (VTE); these events were pulmonary embolism (12 pts, 7.4%), deep venous thrombosis (5 pts, 3.1%), inferior vena cava thrombosis (4 pts, 2.5%). Median time to development of re-thrombosis was 7 months (range 2-13.5 months). Active cancer was the only risk factor significantly associated with recurrent VTE (p = 0.047); pts with prior hysterectomy had a significantly reduced risk of recurrent VTE (p = 0.036). Conclusions: Incidental isolated GVT identified in cancer pts has a high risk of recurrent VTE (13.6%). Based upon specific pts risk factors for VTE, treatment of an incidentally detected GVT in cancer pts with anticoagulation, as per guidelines for other VTE sites, may be indicated.