A symptomatic patient presented to the emergency department with left leg swelling.
The patient underwent an ultrasound Doppler that showed thrombus in the left common femoral vein. As part of the workup for an unprovoked DVT, a CT abdomen and pelvis was performed. This demonstrated a small solid lesion abutting the left external iliac vessels (Fig. 1). The lesion was presumed to be of ovarian origin and a pelvic MRI was arranged for further characterisation. The MRI showed an enhancing tongue of tissue extending from the lesion into the lumen of the external vein (Fig. 2, Fig. 3 and Fig. 4). A suspected diagnosis of external iliac vein leiomyosarcoma was made. This was subsequently confirmed following surgery and pathological assessment.
A leiomyosarcoma is a malignant tumour of smooth muscle differentiation that is encountered within the retroperitoneum and most often has an extravascular pattern of spread. An entirely intravascular pattern of growth is uncommon occurring in only 5% of cases frequently involving the inferior vena cava and renal veins . These intravascular lesions tend to present early due to the compressive symptoms of the mass as occurred in our case. A leiomyosarcoma of the external iliac vein is extremely rare and is a challenging diagnosis for the radiologist due to its location being more consistent for adnexal pathology and lymphadenopathy within the pelvic sidewall.
Leiomyosarcomas are generally a solid mass with well-circumscribed margins however if large they can show areas of haemorrhage and necrosis. At CT the solid components are hyperattenuating to muscle on post-contrast imaging whereas necrotic areas appearing hypoattenuating. These tumours will demonstrate hypointense to isointense T1 signal and high T2 signal with heterogeneous enhancement on post-contrast imaging . As mentioned previously distinguishing this entity from adnexal pathology can be challenging and several signs have been described within the literature that are helpful at separating non-ovarian from ovarian pathology these include the ‘beak sign’ and the ‘embedded ovary sign’. The beak sign indicates that if the mass deforms the edge of an adjacent organ into a ‘beak’ shape it has likely arisen from that organ and the embedded ovary sign suggests that if a mass encases an organ it is presumed to have arisen from that organ [3 & 4]. In our case, the key-imaging finding was the enhancing tissue extending from the lesion into the accompanying vein.
Patients with a leiomyosarcoma are managed in a multidisciplinary fashion in centres with expertise in treating soft-tissue sarcomas. Treatment options involve surgical resection, chemotherapy and radiation therapy. The overall prognosis depends on the stage of disease, adequacy of surgical resection, histological grade and the extent of osseous involvement .
Leiomyosarcoma of the external iliac vein is an extremely rare entity however it is a differential consideration in patients presenting with compressive symptoms and on imaging a soft tissue mass is seen within the pelvic sided wall that abuts this vessel.
Written patient consent for this case was waived by the Editorial Board. Patient data may have been modified to ensure patient anonymity.
 Marko, J. & Wolfman, D.J. 2018, "Retroperitoneal Leiomyosarcoma From the Radiologic Pathology Archives", RadioGraphics, vol. 38, no. 5, pp. 1403-1420. (PMID: 302079636)
Tilkorn, D. J., Hauser, J., Ring, A., Goertz, O., Stricker, I., Steinau, H. U., & Kuhnen, C. 2010, "Leiomyosarcoma of intravascular origin--a rare tumor entity: clinical pathological study of twelve cases.
", World journal of surgical oncology, vol. 8, no. 103, pp. 1477-78. (PMID: 21092216)
 Wachtel, H., Jackson, B.M., Bartlett, E.K., Karakousis, G.C., Roses, R.E., Bavaria, J.E. & Fraker, D.L. 2015, "Resection of primary leiomyosarcoma of the inferior vena cava (IVC) with reconstruction: A case series and review of the literature", Journal of surgical oncology, vol. 111, no. 3, pp. 328-333. (PMID: 25297650)
 Arikawa, S., Uchida, M., Shinagawa, M., Tohnan, T. & Hayabuchi, N. 2006, "Significance of the " beak sign"in the differential diagnosis of uterine lipoleiomyoma from ovarian dermoid cyst", The Kurume medical journal, vol. 53, no. 1-2, pp. 37-40. (PMID: 17043394)
 Shaaban, A.M., Rezvani, M., Tubay, M., Elsayes, K.M., Woodward, P.J. & Menias, C.O. 2016, "Fat-containing Retroperitoneal Lesions: Imaging Characteristics, Localization, and Differential Diagnosis", Radiographics : a review publication of the Radiological Society of North America, Inc, vol. 36, no. 3, pp. 710-734. (PMID: 27163589)