Surgery was performed to diagnose the lesion and to relieve the pain. The patient underwent a L2-L3 laminectomy. A dura mater was exposed, but there was no epidural tumor. A durotomy revealed a highly vascularized, soft, elastic tumor measuring 2.5 × 1.5 × 1 cm. Adhesion was minimal, and the tumor was dissected from the surrounding cauda equine and was excised en bloc (Figure 3).
Histopathological examination revealed thrombus and fibrin clots mixed with tissue fragments; numerous dilated papillary structures of various sizes were found with prominently hyalinized stroma, but findings indicating malignancy such as anaplasia, mitosis, and necrosis were not observed (Figure 4). Immunohistologically, the endothelial cells exhibiting papillary proliferation were positive for CD31 and CD34, thus identifying these cells as vascular endothelial cells. From these findings, the diagnosis of IPEH was reached. Resection of the tumor resolved the patient's symptoms and the Japanese Orthopedic Association score improved from 13 to 29. No recurrence has been observed in the 2-year follow-up period.
IPEH was first reported by Masson1 in 1923 when he identified proliferation of intravascular endothelial cells in a hemorrhoidal vein, calling it “hemangioendotheliome vegetant intravascular.” Subsequently, Clearkin and Enzinger2 recognized that it was not a true tumor and hence named it “intravascular papillary endothelial hyperplasia” in 1976, and the name has been in use ever since. Masson surmised that IPEH occurs due to thrombosis secondary to papillary proliferation of vascular endothelial cells,1 whereas Salyer and Salyer9 postulated that it is a type of reactive lesion in which the vascular endothelial cells proliferate in reaction to thrombus organization.
IPEH is not a true tumor. It occurs in the subcutaneous and soft tissues throughout the body, but is more common in the limbs as well as the head and neck region, which are relatively prone to injury. IPEH in the head and neck region accounts for 10% to 13% of all cases,10 and there are very few reports on its occurrence in the nervous system, particularly the spinal canal, with only four known cases.4 - 7
IPEH has no age predisposition, with slight female preponderance. It often presents as a slow-growing, tender, violaceous cutaneous mass on the head, neck, fingers, and trunk. Deeply situated lesions occur in intramuscular hemangiomas. Although IPEH is benign lesion, it forms expansile and compressive masses.5
IPEH is generally hypervascular and is enhanced by gonadalium. T2-weighted MR imaging generally shows IPEH as hyperintense, whereas T1-weighted imaging typically demonstrates the lesion as hypointense to isointense.11
The histopathological characteristics of IPEH are: (1) papillary proliferation of vascular endothelial cells is localized intravascularly, (2) normal thrombus formation is observed and almost the entire papillary tissue is associated with the thrombus, (3) the vascular endothelial cells are in one or two layers and are not multilayered, (4) almost no abnormalities or mitotic changes are observed in the vascular endothelial cells, and (5) there is no accompanying tissue necrosis.3 This case was diagnosed as IPEH by satisfying four of the above criteria, with the exception that the papillary proliferation was extravascular.
Hashimoto et al3 divided IPEH into three categories based on the differences in occurrence: a primary form that occurs without existing vascular lesions, a secondary form that arises within existing vascular lesions such as varicose veins, hemangioma, or arteriovenous malformation, and an extravascular form that arises extravascularly and is derived from a hematoma. This case was an extravascular form because no preexisting vascular lesions were identified.
Although the pathogenesis of IPEH is still unclear, it is postulated that the trigger may be the formation of a thrombus due to trauma, followed by reactive proliferation of the vascular endothelial cells. IPEH does not exhibit malignant characteristics such as association with malignant neoplasms, metastasis, or invasion. Complete resection is considered the best approach to avoid future local recurrence as long as its location is accessible.12 There have only been four reported cases of IPEH within the spinal canal: Porter et al4 reported an extradural tumor at the level of T6 compressing the spinal cord and Taricco et al5 reported an extradural lesion at the level of T12-L1 compressing the cauda equina. Ali et al6 reported a mass in the posterior epidural space at the T8 level. In three cases, neurological symptoms resolved completely after resection of the lesions and the diagnosis of IPEH was carried out by histopathological examination of the resected tissue. Petry et al7 reported of IPEH involving both the retroperitoneum and the cervical, thoracic, and lumbar spine. In particular at the T10, T11, and T12 levels, spread to the epidural space was associated with mild ventral thecal sac compression demonstrated by MRI. No abnormal cord signal was identified. This is the first report of an IPEH intradural lesion. Although the etiology is not clear, we postulate that an intradural thrombus formed for reasons unknown such as trauma or signs of meningismus or other source of intradural hematoma from which patients are usually symptomatic and resulted in the reactive proliferation of the vascular endothelial cells during thrombus formation. In particular, this lesion extended from the meninges and it may be possible that the tumor in this case was attached to the meninges. Resection of the tumor led to complete resolution of the symptoms and we have not observed any recurrence. Hence, complete resection is recommended when an intradural tumor is suspected to be a vascular lesion.
Here, we reported a case of an intradural IPEH within the cauda equina that was treated with complete resection.
The authors would like to thank Chie Inomoto (Department of Pathology, Tokai University School of Medicine) for supporting our studies.
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Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Orthopaedic Surgeons
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