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Case report

The patient is a 6-year-old girl who presented with a chief complaint of left facial nerve weakness beginning December 2008. Her facial function gradually deteriorated over a period of 10 days. Lyme titers and Epstein-Barr virus titers were negative, and she was diagnosed with idiopathic Bell palsy. The patient was reported to have no history of recurrent acute otitis media, but she had one episode of acute otitis media in February 2009. She complained of increasing dizziness over the same period. The patient denied tinnitus or otalgia and did not subjectively notice any hearing problems. However, an audiogram revealed a left-sided mild to moderate conductive hearing loss and normal right-sided hearing.

Magnetic resonance image (MRI) obtained in May 2009 ( Fig. 1 A, B ) revealed complete opacification of the left middle ear and mastoid. A lobulated mass at the level of the geniculate ganglion measured 1.5 × 1.0 × 1.6 cm and avidly enhanced with intravenous contrast. For further evaluation, a computed tomography scan ( Fig. 1 C, D) revealed an irregularly shaped mass within the region of the geniculate ganglion of the facial nerve with bony erosive changes of the cochlear promontory as well as the stapes. Furthermore, there was dehiscence of the roof of the temporal bone. The lesion was noted to have irregular margins, but did not have the typical honeycombing appearance that is characteristically seen with a hemangioma. The constellation of findings was most suggestive of a facial nerve schwannoma within the geniculate or horizontal segments of the facial nerve.

Hemangioendothelioma. (A and B) Selected magnetic resonance images. The left middle ear and mastoid were completely opacified, and a lobulated mass showed avid enhancement with contrast. (C and D) Selected computed tomography images. The left middle ear mass was irregularly shaped within the region of the geniculate ganglion of the left facial nerve. Bony erosive changes are evident.

The patient was taken to the operating room and underwent a transcanal biopsy in May 2009. The final pathology from the biopsy revealed only nondiagnostic myofibroblastic proliferation. In June 2009, she underwent removal of the tumor off the facial nerve along with a left facial nerve decompression and radical mastoidectomy with fat obliteration and closure of the ear canal via a left transmastoid and middle fossa approach.

The histologic appearance of the tumor demonstrated myofibroblastic cellularity with a rich vascular pattern ( Fig. 2 A, B ). The reticulin stain was the most informative, revealing a robust anastomosing pattern in which epithelioid endothelial cells filled many of the vascular spaces ( Fig. 2 C). Even the CD31 immunostain that stains the endothelial cell surface did not do justice to the epithelioid character of the intravascular elements ( Fig. 2 D). Smooth muscle actin stains revealed concentric smooth muscle fibers around many of the spaces as well as staining in some of the stromal component. The final diagnosis was an epithelioid hemangioma low grade.

Hemangioendothelioma. (A) Spicules of bone are present in a cellular background, slightly spindled, in which occasional dilated vascular profiles are evident (hematoxylin and eosin, ×200). (B) Branching vascular profiles are only slightly more noticeable at higher power (hematoxylin and eosin, ×400). (C) A reticulin stain reveals that the tissue is actually permeated by vascular profiles. Pink-staining nuclear profiles within the spaces belong to the epithelioid endothelial cells (reticulin, ×200). (D) CD31 immunostain for endothelial cells stains the luminal surface of the intravascular endothelial cells (diaminobenzidine, ×400).

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Discussion

The term hemangioendothelioma is used to describe a vascular tumor composed of endothelial cells that can be found in soft tissues as well as bone. These tumors have the capacity to infiltrate into surrounding tissue, recur locally, and metastasize. Hemangioendotheliomas are typically classified as low- to intermediate-grade malignant tumors, but they can behave as benign or malignant tumors and include a variety of tumors with varying malignant potential. Unni et al divided these tumors into 3 grades of malignancy. Low-grade lesions had abundant vasoformation, few mitotic figures, and exhibited little atypia. By contrast, high-grade lesions exhibit more mitotic figures, more atypia, and less vasoformation.

There are several pathologic variants with unique and differing clinical characteristics. Two of the most commonly reported in the head and neck are kaposiform hemangioendothelioma (KH) and epithelioid hemangioendothelioma (EH). KH is a locally aggressive neoplasm that occurs almost exclusively in infants and adolescents . Clinically, kaposiform hemangioendothelioma may appear as tender red plaques, grouped papules, or telangiectasias and is frequently associated with Kasabach-Merrit syndrome that is characterized by profound thrombocytopenia, life-threatening hemorrhage, and lymphangiomatosis . KH exhibits a wide anatomical distribution, affecting skin as well as deep soft tissues. KH exhibits locally aggressive growth with no tendency to regress spontaneously. Histologically, they have irregular infiltrating nodules of compressed vessels that may resemble either capillary hemangioma or Kaposi sarcoma.

Epithelioid hemangioendothelioma was first described by Weiss and Enzinger and exhibits a roughly equal sex distribution. EH is rarely seen in children. EH is most common in superficial or deep soft tissues, but can also occur in liver and bone. Soft tissue lesions are usually unifocal, but liver and bone lesions are often multifocal because of invasive growth along small vessels. Their biologic behavior is typically intermediate between hemangioma and angiosarcoma. Volpe and Mazabraud described EH as having an unpredictable clinical behavior with bones of limbs most commonly involved. Metastases occur in 21% to 61% of cases depending on the location of primary tumor . There are few reports of involvement in the head and neck region .

Grossly, EH exhibit variable coloration; but the tumor is typically reddish-white or gray-white. Microscopically, they are unencapsulated masses and may show vessel lumen filled with tumor cells, necrotic debris, and dense collagen. EHs are composed of short strands or solid nests with rounded or slightly spindled endothelial cells. Cytologically, they display mild atypia with rare mitotic activity . Lesions with increased atypia and mitotic activity may indicate a more aggressive clinical course. Immunohistochemically, EH exhibits a vascular phenotype with positive staining for the endothelial markers CD31, CD34, and von Willebrand factor. Approximately 25% of lesions express cytokeratin, which may lead to misdiagnosis of nonvascular lesions .

Hemangioendotheliomas are reported to have an aggressive destructive tendency radiologically, particularly in the temporomastoid region. Magnetic resonance imaging may exhibit isointense T1-weighted images and hyperintense T2-weighted images, as well as moderate enhancement with intravenous gadolinium . The differential diagnosis for these findings includes paraganglioma, hemangioma, and granulation tissue. Because there are no reliable clinical or radiological signs, definitive diagnosis is usually made by examining tissue after biopsy or surgical resection. A recent study showed enhanced fluorodeoxyglucose uptake on positron emission tomography for pulmonary hemangioendothelioma .

Given the unpredictable disease course for hemangioendotheliomas, most reports advocate wide surgical excision, often with postoperative radiation therapy. The tumor is reported to be radiosensitive , with cure by radiation therapy alone; but this treatment strategy should be reserved for patients with unresectable tumor. Orchard et al also reported successful treatment with α -interferon of 2 infants with hemangioendothelioma, one of which was located in the head and neck. The mechanism of action for interferon in these cases was suggested to be the antagonism of various growth factors.