Papillary endothelial hyperplasia (PEH) is a multilobular vascular tumour with areas of thrombosis and occasional calcification. This tumour can masquerade as other benign or malignant tumours both clinically and pathologically, including angiolymphoid hyperplasia with eosinophilia (Kimura disease) and angiosarcoma (Pins et al. 1993). The differentiation relies on histopathologic differentiating features that can often be subtle (Pins et al. 1993).
Papillary endothelial hyperplasia is classified into three subtypes depending on the vasculature, including primary (or pure) subtype with the lesion arising in dilated vessel, secondary (or mixed) subtype with the lesion developing in a pre-existing vascular tumour and extravascular subtype, the most uncommon, in which the lesion develops in the bed of a haematoma (Hashimoto et al. 1983; Pins et al. 1993). Ocular or orbital involvement by PEH is rare (Pins et al. 1993).
A 40-year-old Chinese man with known Behçet’s disease of the retina initially manifesting as panuveitis and retinal vasculitis was in remission following 3 months of systemic prednisolone. He developed a painless left brow mass over 7 months. He denied trauma but vaguely recalled left eyebrow surgery 10 years previous for possible tumour. There was no follow-up or pathology information.
On examination, there was a poorly circumscribed, diffuse, nontender infrabrow mass of 3 cm diameter (Fig. 1A). By palpation, the mass was trilobed and minimally mobile in the subcutaneous tissue. There was no bruit.
Orbital computed tomography revealed a circumscribed preseptal medial eyelid mass with intralesional calcification and no bone erosion (Fig. 1B). Excisional biopsy disclosed a multilobulated purple mass with foci of calcification. On microscopy, there was vascular thrombosis with no evidence of malignancy. A second pathology opinion revealed fibrovascular tissue with thrombosed vascular spaces. Some of the thrombi were calcified and fibrotic (Fig. 1C). There were fronds of papillary projections lined by a single layer of plump, cytologically bland endothelial cells surrounding a fibrin core (Fig. 1D,E). Some central cores were hyalinized and contained fine vessels (Fig. 1F). The papillary fronds merged at the base with granulation tissue, forming irregular, arborizing vascular clefts (Fig. 1D). There was no tissue necrosis, inflammation, nuclear pleomorphism or mitotic activity. These features were consistent with extravascular PEH or Masson’s tumour.
Extravascular PEH is an uncommon vascular tumour that can masquerade as a benign or malignant solid tumour. This tumour most often occurs in the head and neck region (23%), lower extremities (17%) and fingers (16%) (Pins et al. 1993). The putative factors related to the development of PEH include oestrogenic hormonal influence, deranged paracrine signalling or inappropriate cytokine-like fibroblast growth factor stimulation (Pins et al. 1993). Trauma is usually a prerequisite for the formation of extravascular PEH. Some theorize that it is the result of exuberant organization and recanalization of a thrombus rather than a primary process with secondary thrombosis (Pins et al. 1993).
Papillary endothelial hyperplasia can simulate angiosarcoma as both share histopathologic architecture including extravascular location, papillary formation, anastomosing vascular channels and plump endothelial cells (Pins et al. 1993; Branton et al. 2003). The differentiating features predominantly include the absence of features in PEH but present in angiosarcoma including pleomorphism, atypical mitotic figures, endothelial multilayering, tissue necrosis and irregular, infiltrative anastomosing vascular channels invading the surrounding tissues (Pins et al. 1993; Branton et al. 2003). Another differentiating feature is the occasional presence of pre-existing vascular tumour in which PEH develops, but the lack thereof does not exclude PEH. Extravascular PEH is notably devoid of pre-existing vascular lesion (Pins et al. 1993). Extravascular PEH can also mimic a simple thrombotic process with associated calcification or fibrosis, as happened in our case (Pins et al. 1993). The histopathologic differentiation of these conditions is prognostically important.
The relationship of PEH with our patient’s underlying Behçet’s disease remains unknown. Behçet’s disease is a systemic autoimmune disease with ocular (uveitis, vasculitis, retinitis, vascular occlusion, optic neuropathy, glaucoma and cataract) and systemic (recurrent oral/genital ulcers, recurrent deep vein thrombosis and other thrombotic tendency with thrombophlebitis, dermatographism and pathergy phenomenon) manifestations. Patients with Behçet’s disease are at risk for vascular thrombosis. In a multicenter review of 661 cases of Behçet’s disease from Turkey, there were no cases of PEH (Alpsey et al. 2007). In our case, we speculate that the underlying Behçet’s disease in our patient could explain the spontaneous eyelid thrombosis and extravascular PEH.