교신저자：김재명, 405-760 인천광역시 남동구 구월동 1198  가천의과학대학교 길병원 신경외과학교실
교신저자：전화：(032) 460-3304 · 전송：(032) 460-3899 · E-mail：jmkim@gilhospital.com

Introduction

   Intramuscular hemangiomas (IMH) are uncommon tumors in the head and neck region. The masseter and trapezius muscle are the most frequent site. Because of rarity and unfamiliar presentation, preoperative diagnosis and proper treatment modality are usually in troublesomeness. There are several cases of IMH in masseter and buccinators muscle in Korea.^{1,2,3,4,5,6,7,8,9)} But, IMH in temporalis muscle were rarely reported.^8,9) This paper present a rare case of IMH of temporalis muscle in young male with review of the literatures.

Case Report

   A 24-year-old young man presented with soft, painless left facial swelling that had been noticed by himself a few days ago. There was no history of prior trauma. The swelling was centered over the temporal fossa, extending to the left temporomandibular joint. Radiological evaluations were recommended, but he refused any evaluations. After 1 month later, he was referred with increased swelling and tenderness. Physical examination revealed a slightly hard, large and deep mass approximately 6 cm in length (Fig. 1). There was no overlying skin discoloration and bruit or thrill. Facial nerve palsy was not seen. Preliminary diagnosis included organizing hematoma, thrombosed hemangioma, soft tissue sarcoma, neurogenic tumor, and so forth.
   Plain radiography (not shown here) showed no gross bony abnormalities, and there was no calcification. Magnetic resonance imaging (MRI) showed a large soft tissue mass within the left temporalis muscle (Fig. 2). The mass was hyperintense relative to the muscles on the T2 weighted images and isointense on the T1 weighted images. There were multiple vascular signals in the mass on ultrasound sonography (Fig. 3). Fine needle aspiration (FNA) was not taken because of bleeding risk. Preoperative external carotid angiography showed a blood-pooling space supplied from a small arterial branch of left superficial termporal artery (Fig. 4). The mass was very slowly pooled with contrast material. A diagnosis of muscular hemangiomas was made.
   Surgical exploration was performed under the general anesthesia. About 6 cm-sized linear vertical skin incision was made above the zygomatic arch. Subcutaneous tissue was dissected, and branches of facial nerve were retracted. The mass was entirely within the left temporalis muscle with poorly demarcated boundary. There were numerous vascular channels within the mass. There was mild to moderate blood loss during the operation, and the branches of the facial nerve remained intact. The patient made an uneventful postoperative recovery, and functional and cosmetic results were good.
   Histological examination revealed numerous dilated blood vessels with a thrombus within muscle fibers (Fig. 5). The definitive diagnosis was a cavernous intramuscular hemangioma. Postoperative follow-up during a 5-month period revealed no recurrence.

Discussion

   Hemangiomas are benign, vascular tumor, mainly congenital, affecting skin and subcutaneous tissue.¹⁰⁾ IMH are rare, accounting for less than 1% of all hemangiomas. They occur most frequently in the skeletal muscles. Only about 14% of IMH develop in the head and neck region. IMH within temporal muscle is reported only a few cases until now.^{10,11,12,13,14,15,16,17,18)} IMH are encountered mostly at the third decade, and there is no sex predominance.¹¹⁾ The most common presentation is a smooth, mobile, soft tissue swelling that may fluctuate in size. The lesion usually does not exhibit any of the vascular signs such as thrill or skin discoloration that are characteristic of superficial hemangiomas. The rarity of the lesion causes it to be ignored in a differential diagnosis, and it is commonly confused with benign or malignant neoplasm of the muscle, neurofibroma, or aneurysm.¹²⁾ Plain X-ray films, CT scan, angiography may not be specific for this tumor. The differential diagnosis could be made easily with MRI. The low-signal intensity with the T1 weighted imaging and in the fat free zone negated the diagnosis of an angiolipoma, which presents as high-signal intensity.¹¹⁾ The enhanced contrast medium indicating high vascularity negated the diagnosis of lymphoma.¹¹⁾ 
   The most accepted theory of the pathogenesis is that it is a congenital mass of abnormal embryonic sequestration.¹⁰⁾
   The most accepted theory of the pathogenesis is that it is a congenital mass of abnormal embryonic sequestration.¹⁰⁾ 
   IMH had been classified by Allen and Enzinger according to the caliber of the compositional vessels.¹⁹⁾ Three types of IMH are recognized：1) small vessel or capillary type (diameter<140 μm)；2) large vessel or cavernous type (diameter>140 μm)；and 3) mixed type, consisting of both. The small vessel type accounts for 30% of IMH in the head and neck；the large vessel and mixed types appear in 19% and 5%, respectively. The mixed type carries the highest recurrence rate (28%), followed by the small (20%) and the large vessel types (9%). Rare microscopic features include mitotic activity, intraluminal papillary tufting, and perineural infiltration by capillary vessels. Despite such findings, the tumors are completely benign and have never been shown to metastasize. The recurrence rate is relatively high even after wide surgical excision, due to its microscopically infiltrative pattern of diffusion into the surrounding muscular tissue. 
   Treatment modalities were variable depending on the localization, size, vascularization and clinical symptoms.¹³⁾ Preoperative embolization can help to reduce intraoperative bleeding.²⁰⁾ But, In this case, embolization was not performed because of relatively slow, small amount of blood pooling. Radiation therapy can help in their suppression of the mass and the hindrance of the enlargement of the residual mass, but not in the primary treatment.¹⁴⁾ Among these modalities, surgical excision of the mass with resection of the surrounding muscle is the best treatment. 
   Long-term clinical and radiological follow-ups are strongly recommended because of high recurrence rate.¹⁵⁾ 

Conclusion

   This case showed a cavernous IMH involving temporalis muscle in young adult. MRI is the most reliable study for this lesion, and complete surgical excision with meticulous bleeding control is required to prevent intraoperative bleeding and local recurrence.

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