Intramuscular hemangiomas (IMH) are vascular tumors of unknown origin, benign and uncommon represent less than 1% of cases of hemangiomas, most often located in the skeletal muscles of the trunk and limbs . Only 10% of intra-articular hemangiomas are located on the face and neck . When they are present on the head, the masseter localization is the most frequent although it represents only very few cases, that is 0.8% of all hemangiomas . Clinically, intramuscular hemangiomas frequently present as a mass of soft tissue located near or in the parotid space, which gradually enlarges, rarely associated with clinical signs suggestive of a vascular origin . This mass sensation may or may not be accompanied by pain. The intramuscular hemangioma is rarely evoked as the first diagnosis whereas we gladly retain that of a parotid tumor first. We report a case of intramuscular hemangioma lesion occurring in projection of the masseter region.
A 30-year-old woman presented to the maxillofacial and radiology department with a complaint of incidental discovery of a right cheek mass with slow and progressive growth for 3 years. The patient had no particular known medical and family history or facial trauma. On physical examination, it was a solitary, oblong-shaped, well-defined, hard, painless, non-throbbing mass that appeared suddenly on contraction of the masseter muscle. There was no fever, inflammatory sign, or collateral venous circulation. Skin color was normal. The intraoral examination was unremarkable. On ultrasound, we find an intramuscular lesion, oblong, heterogeneous isoechoic seat of hypoechoic zone, well limited, showing intralesional vascularization on color Doppler (Figure 1a-b). Magnetic resonance imaging (MRI) objectified an intramuscular mass of the right masseter, well limited of 11 x 8mm, in T1 hyposignal, T2 hypersignal, site of a punctiform structure in hyposignal on all the sequences (Figures 2-4) and gradually increasing after injection of gadolinium (Figure 5). It showed no detectable connection with the surrounding vascular structures. These results were strongly suggestive of an intramuscular hemangioma of the masseter muscle. seat of a punctiform structure in hyposignal on all the sequences (Figures 2-4) and enhancing gradually after injection of gadolinium (Figure 5). It showed no detectable connection with the surrounding vascular structures. These results were strongly suggestive of an intramuscular hemangioma of the masseter muscle. seat of a punctiform structure in hyposignal on all the sequences (Figures 2-4) and enhancing gradually after injection of gadolinium (Figure 5). It showed no detectable connection with the surrounding vascular structures. These results were strongly suggestive of an intramuscular hemangioma of the masseter muscle. The patient was informed of her condition and treatment options were discussed. She also chose to forgo treatment at that time.
Intramuscular hemangiomas are rare and 10% concern the head and neck region. The masseter muscle is the most involved, although few cases have been reported .
Intramuscular hemangiomas are benign, congenital tumors for which heredity plays no role and for which the racial factor does not exist. They are more often observed in adolescents and young adults in whom, in 90% of cases, the diagnosis is made before the age of 30 .
Excessive muscle contractions and trauma seem to be important factors in the development of this type of malformation [1,3].
Hormonal factors would also play a role. Indeed, there is a clear increase in volume of these tumors during menarche, pregnancy and menstrual cycles, which explains a slight female predominance for this type of tumor  although the location at the masseter, the majority cases are diagnosed in humans .
In nearly 70% of cases, intramuscular hemangiomas are located in only one muscle . It is a mass of variable size, unique, mobile, of rather firm consistency, associated in more than half of the cases with intermittent pain due to muscle compression .
Exceptionally, the skin may have a bluish tint, with increased local heat related to hypervascularization .
The beating character and the auscultatory thrill are also exceptional, as they are often masked by the thickness of the superficial muscular layer .
Also, it is very rare to observe an increase in the size of the swelling, when the head is tilted forward or “Wattle's sign”, which is a strong indication of the diagnosis .
It should be noted that this semiology is present in the masseter localizations only in the event of superficial and voluminous tumour. Imaging is useful for the intraoperative diagnosis of these lesions.
The standard X-ray can reveal the existence of phleboliths which must be distinguished from intra parotid salivary stones. Echo-Doppler is an examination that confirms the vascular nature of the mass, but is not efficient enough to precisely define its limits and its relationship with neighboring tissues [2,7].
The CT scan without injection of contrast product may show an ill-defined mass, of similar density to the muscle, as well as very small phleboliths that cannot be observed on standard radiography. After contrast, significant enhancement is typical .
MRI is currently the ideal imaging technique for diagnosing soft tissue hemangioma .
On T1-weighted sequence, hemangiomas are isointense or hyperintense to muscle tissue with blurred margins. On the T2-weighted sequence, they are usually hyper-intense and have clear margins and lobulated outlines [9,10]. The marked hyper-intensity of T2 lesions is due to increased fluid content secondary to stagnation of blood flow in the large vessels . The areas of hemorrhage and calcification as well as the adipose tissue located in the hemangioma are responsible for the heterogeneous intensity of the signal on the T1- and T2-weighted sequences. Pitted or reticular areas of low signal intensity represent fibrous tissue, rapid vascular flow, or foci of calcification. Phleboliths appear as circular areas of low signal intensity [9,10]. Significant tumor enhancement is expected when gadolinium contrast products are used .
Arteriography is only indicated in large tumours. It makes it possible to identify the arterial pedicles that supply the tumor and preoperative embolization, thus reducing the risk of intraoperative bleeding .
Management is done on a case-by-case basis, taking into account the size and anatomical accessibility of the tumour, its growth rate, the patient's age, aesthetic and functional considerations . Several types of treatment have been suggested (injections of steroids, radiotherapy or sclerosing agents, cryotherapy and electrocoagulation), but surgical resection remains the optimal means due to the infiltrating nature of intramuscular hemangiomas . Despite this approach, reported local recurrence rates are lower.
Intra masseter hemangiomas are rare tumors often mistakenly considered as parotid tumors. The essential radiological examinations before treatment are CT or MRI. Treatment should be individualized taking into account the patient's clinical condition, but surgery is the reference treatment with different possible approaches.
Conflicts of interest
The authors declare no conflict.