Intravascular Papillary Endothelial Hyperplasia
Intravascular papillary endothelial hyperplasia (IPEH), or Masson’s tumor
Intravascular papillary endothelial hyperplasia, also known as Masson’s tumor, is a benign intravascular lesion that can mimic other benign lesions and even some malignancies. First described in 1923 by French pathologist Pierre Masson as “vegetant intravascular hemangioendothelioma,” IPEH most commonly presents in subcutaneous tissue as a small, firm lesion with a bluish color; it can gradually increase in size and may also be tender to palpation.  This lesion is uncommon, with approximately 200 case studies reported in the literature. Even fewer cases, specifically 24 across 16 unique publications, have been described involving lesions of the orbit, periorbital area, or ocular adnexa.               Two additional case reports describe intracranial lesions near the superior orbital fissure that presented with symptoms of cranial nerve compression.  Despite the benign nature of IPEH, it can have a significant impact on health depending on where in the body it occurs.  
IPEH typically presents in adulthood, but lacks a strong predilection for age, race, or sex. A small number of childhood cases has been reported.
Etiology and Pathophysiology
IPEH can occur as a primary vascular lesion, or it can be superimposed on a preexisting malformation. It is classified into one of three types based on etiology:
- Type I: the primary form, also known as the “pure” form, arising in a dilated vessel
- Type II: the most common type, also known as the “mixed” form; occurs in association with a thrombus in the setting of a preexisting lesion, e.g. within a hemangioma, arteriovenous malformation, pyogenic granuloma, or varix
- Type III: the very rare extravascular form, occurring in a hematoma usually after trauma
Overall, the pathogenesis of IPEH remains ill-defined. Various authors suggest that it is either a primary, reactive endothelial proliferation with secondary thrombosis, or thrombosis with secondary reactive endothelial proliferation. It may represent an unusual variant of thrombus organization, and in some cases it may be associated with preceding trauma.   There is no known pattern of inheritance.
IPEH occurs most commonly in skin and soft tissue, usually in the head, neck, and extremities. One report estimated that it accounts for approximately 2% of vascular tumors of the skin and subcutaneous tissue.
IPEH has been rarely observed in the oral cavity. Extremely rare involvement has been reported in various organs, including the kidney, bone, heart, liver, knee joint, genitalia, urethra, spine, and brain.
Ocular manifestations of IPEH are uncommon, and mostly involve lesions of the eyelid and periorbital area. More rarely, lesions within the orbit have been observed.
The definitive diagnosis of IPEH must be made by biopsy and histologic examination. Clinical manifestations vary with different organ involvement.
Most cases of IPEH develop within the vasculature of the deep dermis or subcutaneous tissue, sometimes preceded by trauma, to present as a benign, firm, painless, reddish-purple vascular tumor. In some cases, the lesion may grow slowly, be tender to palpation, or be multi-lobulated.
Ocular symptoms of IPEH can manifest acutely or insidiously. When ocular involvement occurs, patients may present with orbital pain, proptosis, decreased visual acuity, ptosis, restricted extraocular muscle movement, optic disc edema, diplopia, conjunctival injection, eyelid swelling, ectropion, and sensory deficit secondary to nerve compression.    
Exceedingly rare intracranial IPEH has presented with ocular findings. A 1992 case report by Patt et al discusses a 27-year-old female with an IPEH lesion at the left superior orbital fissure. The patient presented with headache and abducens nerve palsy, and her symptoms resolved completely after surgical excision. Similarly, a 2005 case report by Ohshima et al discusses a 41-year-old female with an IPEH lesion at the left superior orbital fissure. The patient presented with a 1-year history of progressive abducens nerve palsy and facial sensory loss; half of her lesion was resected surgically for biopsy, and the remaining tumor was successfully treated with gamma knife radiosurgery with no recurrence at 2 years post-op.
Diagnostic procedures include:
- Biopsy and histopathologic examination: crucial to diagnosis. Typical histologic characteristics of IPEH include intravascular papillae composed of connective tissue, covered in endothelial cells, with a variable amount of thrombus present. Diagnosis of IPEH is complicated by microscopic similarities to angiosarcoma. However, unlike many malignancies, IPEH is entirely intraluminal and does not erode the vascular wall or invade adjacent tissues. IPEH occurs in close association with an organized thrombus. Furthermore, IPEH does not feature tissue necrosis or malignant cytological features. 
- Cytology: to evaluate for possible malignancy, since IPEH classically mimics angiosarcoma
- Imaging: magnetic resonance imaging (MRI) and computed tomography (CT) to detect lesions; radiographic images may be indicated when, in rare instances, bone or joint involvement is suspected
Note: Because immunohistochemistry fails to differentiate IPEH from angiosarcoma, it is not recommended in diagnosis.
- Kaposi sarcoma
- Pyogenic granuloma
- Pleomorphic adenoma
- Thrombosed vein
- Traumatic fibroma
- Lacrimal sac mass
The preferred treatment for IPEH is complete surgical excision. Other approaches, including gamma knife radiosurgery and chemotherapy in cases of incompletely excised or multiple intracranial lesions, have been successful in a limited number of documented cases.
Prognosis and Complications
The prognosis for patients with IPEH is generally quite good. However, depending on the location of the lesion, quality of life can be significantly diminished by complications of delayed treatment. For example, a 2012 case report by Fasina et al reports a 14-year-old male who had progressively worsening right proptosis beginning shortly after birth. After successful excision of the responsible orbital IPEH lesion, he suffered persistent proptosis, loss of visual acuity, and impairment of ocular motility. This case suggests that early diagnosis and treatment of orbital, periorbital, intracranial, and other lesions may help prevent irreversible deficits.
Recurrences of IPEH have been reported in cases of incomplete surgical excision.
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