Teaching Case

Previously healthy 12-year-old patient came to our attention for abdominal pain localized in the right upper quadrant of the abdomen. The remaining clinical examination and laboratory tests were within the normal limits, except for mild eosinophilia; furthermore, there were no alteration in hepatic, renal and coagulation function markers.

An abdominal echography was performed showing a round shape filling defect (8 x 6 mm) in the suprarenal tract of the inferior vena cava, with a normal aortic, portal and hepatic vein vascularization. (Figure 1)

To further investigate this finding, a computed tomography (CT) scan with contrast medium and a Magnetic Resonance (MR) were performed. The CT showed an endoluminal round shape formation with mild enhancement in arterial phase and hyper-density in venous phase.The characteristics of the lesion were not specific, so a thrombus or a vascular malformation were suspected. Dimer-test were within the normal range and patients was then admitted in surgical ward to perform the excision of the lesion. The subsequent cytologic examination gave the diagnosis of a pyogenic granuloma.

 Lobular capillary hemangioma (LCH), also named pyogenic granuloma (PG) is a benign tumour that usually develops on the skin or mucous and shows polypoid growth [1]. Intravenous pyogenic granuloma (IVPG) is a subtype of LCH that usually develops in the veins of the neck and upper extremities, such as the jugular vein, cephalic vein, azygos vein, and some special areas like the renal vein [2]. It was first described in 1979 by Cooper et al. [3]. IVPG arising from the inferior vena cava is extremely rare with few cases reported in the literature [4]. The clinical features are not characteristic to suggest the diagnosis, as IVPG may be an incidental finding or asymptomatic mass. This solid tumour presents a polypoid form composed of epithelioid-appearing endothelial cells [5]. It can be considered a variant of the PG of the extremities in which the capillary proliferation is entirely confined within a vein lumen. The pathogenesis of IVPG remains unclear, with a neoplastic process favoured [6].

On ultrasound (US) imaging, IVGP appears as a nodular hypoechoic lesion with regular margins connected to the vessel wall by a stalk and vascular spots on colour Doppler. These US features should lead to suspect IVGP rather than an intraluminal thrombus.

On MRI, this lesion is usually isointense to muscles on T1-weighted images with variableT2 signal.

Differential diagnosis include venous thrombosis, neural lesions or extrinsic compression lesions, and other vascular neoplasms. Venous thrombosis usually shows a filling defect or absence of flow within a vessel and is hypointense to muscle on T2-weighted images [5].

However, the histologic examination is necessary to rule out malignancy. At histological examination, two different patterns of IVPG have been described: the typical uncomplicated lobular pattern of capillaries with small lumina and the edematous pattern with stromal infiltration by

inflammatory cells and dilated vessels [3]. The typical feature of IVPG includes an intraluminal polyp attached to the vein wall and composed of lobules of capillaries lined by flattened or rounded endothelial cells [5].

The treatment of choice is the complete surgical excision with a small portion of the vein, and the prognosis is excellent.

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