Cavernous hemangioma of the masseter muscle

Clinical History

A 26-year-old female patient presented with a slowly growing swelling at the mandibular angle of the left cheek for the past 6 months (Fig. 1). The swelling increased in size during clenching of the cheeks and the overlaying skin could be moved easily over the swelling. There was no pain.

Imaging Findings

An MRI was requested for evaluation of the lesion's extent and for further characterization. This examination revealed an intramuscular mass, contained within the fascia of the left masseter muscle. The margins were polylobulated, resembling a "bunch of grapes" (Fig. 2). The lesion was of high signal on FS T2-weighted images (WI) (Fig. 2) and isointense to muscle on T1-WI (Fig. 3a). After intravenous administration of gadolinium contrast, heterogeneous peripheral enhancement was seen (Fig. 3b). The lateral aspect of the lesion contained a hypointense nodule, in keeping with a small phlebolith (Fig. 2, 3b).

Because of an increase in size, the lesion was explored surgically. Histopathological examination of the resection specimen showed large thin-walled vascular structures surrounded by striated muscle tissue (Fig. 4a). A small phlebolith was also found (Fig. 4b).

Based on the imaging and histopathological findings, the diagnosis of a cavernous haemangioma of the masseter muscle was made.

Discussion

Haemangiomas are benign vascular tumours. They consist of a purposeless proliferation of blood vessels. There are two main histological types of haemangiomas. Capillary haemangiomas are the most frequent and consist of small disorganized blood vessels with large endothelial cells. Cavernous haemangiomas consist of dilated thin-walled tortuous vessels with flattened endothelial cells. Mixed variants may occur as well. [1, 3]

Haemangiomas are usually confined to the skin. Only 1 % of all haemangiomas are located within muscle tissue. Ten percent of these intramuscular haemangiomas (IMH) affect the head and neck region. The most frequent location in the head and neck region is the masseter muscle. [1, 2] The precise aetiology remains unclear but trauma, excessive muscle contractions and hormonal factors seem to be important pathogenetic factors. [2]

Correct diagnosis of lesions at the mandibular angle solely based on clinical evaluation is difficult. Clinically, an IMH is most commonly mistaken for a parotid gland tumour, a lymph node or a lesion originating from branchial cleft remnants. In case of an IMH, a wattle sign may be seen, consisting of increasing size in dependent head position or during Valsalva. This sign has a high specificity but has a low sensitivity. [1, 2, 3]

Imaging is important in the diagnosis of a cavernous haemangioma of the masseter muscle. Plain films are usually noncontributive, but may show phleboliths, to be distinguished from sialoliths. Phleboliths are the result of stasis of blood in the tortuous vessels and occur in 3% to 50% of IMHs. CT can be used for further differentiation between phleboliths and sialoliths. [1, 2] The presence of intralesional phleboliths is a useful clue towards the diagnosis of IMH. [3] On the contrary, lymphangiomas do not contain phleboliths, usually extend in multiple compartments and are seen in a younger population. [4]

MRI is the preferred imaging modality for local staging and characterization. Morphologically, the lesion resembles a "bunch of grapes". IMH are hyperintense on T2-WI due to the free water present in stagnant blood. Phleboliths are round foci of low signal on all pulse sequences. The enhancement pattern is variable. [1, 2, 3]

Treatment of a cavernous haemangioma is only required in case of lesion's growth, loss of function of the adjacent tissues, pain, cosmetic issues or necrosis. Surgical resection yields the best result. Sclerotherapy, radiation therapy, cryotherapy, laser therapy, embolization and ligation of the feeding vessel have also been reported. [1, 2, 3]

Differential Diagnosis List

Final Diagnosis

Cavernous haemangioma of the masseter muscle

URL:	https://www.eurorad.org/case/11592
DOI:	10.1594/EURORAD/CASE.11592
ISSN:	1563-4086