Teaching Case

A 61 years-old woman complained of progressive pelvic pain for 4-months, with no abnormal vaginal bleeding. Physical examination only revealed a distended abdomen, with no pain on compression. On the gynecological observation the vagina and cervix were unremarkable.

Pelvic post-contrast computed tomography (CT) revealed a large, well defined but markedly heterogeneous tumor in the uterine fundus, partially exophytic, with small coarse and peripheric calcifications, which was suggestive of subserosal leiomyoma. However, there was a tubular lesion with the same characteristics in the right parametrium, extending superiorly into the retro-peritoneal iliac vessels.

On magnetic resonance (MR) imaging both tumors were iso-intense to muscle on T1-weighted imaging (T1W) and heterogeneously hyper-intense on T2-weighted imaging (T2W). The fundus lesion was irregularly delineated with a hypo-intense layer of myometrium, and the tubular right parametrial lesion showed well-defined borders with lobulated contours. This lesion extended from the para-cervical region into the primitive iliac vessel's region, inducing pelvic venous congestion with some peri-uterine transudation. Both lesions demonstrated restricted diffusion, and almost homogeneous intense enhancement after gadolinium administration. Neither pelvic adenopathies nor distant lesions were documented.

Intravenous leiomyomatosis (IVL) is a rare manifestation of a benign uterine leiomyoma [1]. IVL is an aggressive form of this benign condition, representing growth of smooth muscle within the lumen of vessels, outside the limits of a uterine leiomyoma [2]. It can grow from the walls of the vein itself, but most commonly arises from an uterine leiomyoma, growing into the uterine vessels [3]. From here, tumor can extend upwards into the right atrial cavity [3], giving different clinical symptoms depending on the level of the tumor, ranging from asymptomatic, to pelvic pain and vaginal bleeding (typical leiomyoma symptoms), to leg edema and swelling from iliac vessels/inferior vena cava occlusion, and to cardiac failure, dyspnea and even syncope or sudden death from cardiac extension [2-4].

The radiologic diagnosis is suggested when a parametrial lesion with growth along pelvic and retroperitoneal vessels is present, with similar characteristics on MR and CT of a uterine leiomyoma, being confirmed when a connection between the two is seen [3-4]. The presence of coarse calcifications may help to establish the diagnosis. However, these may be mistaken with phleboliths, typically located in the pelvis. Many cases are found after previous hysterectomy for leiomyomas, which may be a clue for this entity, but also hinder the radiological connection sign [3]. MR with gadolinium administration is of uttermost importance, mainly to differentiate IVL from a bland venous thrombus, but also because IVL is usually very vascular [2]. The typical MR signal characteristics are iso-intensity to muscle on T1W, and iso- to hypo-intensity on T2W [1, 3, 4]. Hydropic degeneration is the most common degeneration of IVL [2], which translates into hyper-intensity on T2W.

If IVL reaches the inferior vena cava, other tumour thrombus type of lesions must be considered: Wilms tumour, hepatocellular carcinoma and adrenocortical carcinoma [3, 4].
Treatment of choice is complete surgical excision, which includes total hysterectomy, bilateral oophorectomy (hormonal dependent tumor) and excision of the vessels involved, sometimes even with cardiotomy [1, 3, 4]. Considering 30% of recurrence, long-term imaging follow-up at 3-6 months interval is recommended [4].

IVL is a rare form of a leiomyoma, that can manifest clinically from asymptomatic to sudden death, with similar imaging characteristics. Surgical excision is the norm, and follow-up is advocated attending to its high recurrence rate.

Written informed patient consent for publication has been obtained.