Clinical, Imaging and Histopathology of Angioleiomyoma of the Buccal Cheek

Angioleiomyoma is a benign neoplasia originating from vascular smooth muscle and very uncommon in the oral cavity. In this report, we present a rare case of angioleiomyoma in oral cavity in a 46-year-old female buccal cheek and discuss the clinical, histological, and immunohistochemical characteristics. As the treatment of choice is the complete excision, the lesion was excised under local anesthesia with no further complications. In addition, a brief update on other reported cases of angiomyoma in the oral cavity is further discussed.


Introduction
Angiomyoma or angioleiomyoma (also known as vascular leiomyoma) are benign neoplasms originating from vascular smooth muscle [1,2]. Histologically, there are subgroups in three categories: solid, venous, and cavernous [3]. They commonly occur in the extremities and female genital tract and rarely in the oral cavity [4,5]. The most common site in the oral cavity is in the lips [1]. Other reported sites were the palate, tongue, cheek, gingiva, retromolar area, and submandibular triangle [2,[6][7][8][9][10]. Although the etiology is still unclear, previous studies report trauma or spontaneous development as the causes of origin in oral cavity [10,11]. The lesion is most often detected in adults of 30 to 50 years old [3]. Clinically, it usually presents as a slow growing, painless nodule or mass of variable size; however, pain has also been reported [12]. The final treatment and diagnosis is based on surgical excision and hematoxylin and eosin (H&E) staining and immune-histochemical (IHC) assessments [1]. In this report, a rare case of angioleiomyoma in the cheek along with a complete imaging assessment including color Doppler ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) with an update on the literature is presented.

Case Report
A 46-year-old female was referred to a private clinic of an Oral and Maxillofacial Surgeon with complaint of a painless swelling in the right side of her cheek since 6 years ago. The swelling was initially small in size and slowly enlarged, although the patients faced no tenderness in the area. The patient had diabetes mellitus and anemia. In addition, no history of previous trauma to the area was present. Extraoral examination showed no asymmetry or marked expansion on the right cheek. On intraoral examination, no clinically visible lesion was detected. The mucosa was intact with no color change. When the area was palpated, a firm, compressible solid mass was detected with moderate attachment to the adjacent tissues. The estimated size of the lesion was 1:5 * 1 cm, and the approximate diameter was 1.5 cm. No pulsation or bruit was present. The patient had previously visited and had prior imaging including Doppler ultrasonography, multidetector computed tomography (MDCT), and MRI. The results of ultrasonography indicated a well-defined hypoechoic heterogeneous mass lying beneath the skin measuring 13 * 18 mm ( Figure 1). The lesion had moderate vascular flow. MDCT showed a circular well-defined homogenous mass over the buccinator muscle ( Figure 2). The MRI T1 sequence showed a well-defined low signal mass between the buccinator muscle and buccal fat (Figure 3(a)). The MRI T2 sequence showed that the mass is homogenous and high signal (Figure 3(b)). A soft tissue mass was suspected, and an intraoral surgical excisional biopsy was planned. Upon obtaining consent, an excisional biopsy was performed under local anesthesia and incision was made on the buccal mucosa just over the palpated mass ( Figure 4). The lesion was completely excised ( Figure 5). H&E staining histopathological examination demonstrated an encapsulated mass composed of fully developed cavernous angioma in a fibrous stroma and occasionally myxomatous change. The thin-wall blood vessels showed papillary projections to the lumen which some had become irregular, large in size, and even sinusoid in some areas ( Figure 6(a)). The stroma contains immature spindle-shaped fibroblasts with a paralleling fasci-cle pattern next to the blood vessels ( Figure 6(b)). The mixed inflammatory infiltration and hyalinized area intermixed with adipose tissue were also found. In the IHC staining analysis, the specimen was positive for both SMA (smooth muscle actin) (Figures 7(a) and 7(b)) and desmin (Figures 7(c) and 7(d)); however, the microscopic features in combination with IHC findings were consistent with angioleiomyoma diagnosis. A postoperative follow-up of the patient was uneventful. The area had healed with no complication, and no signs of recurrence were detected.

Discussion
Angioleiomyoma is a rare benign soft tissue neoplasm of oral cavity [7]. Although hormonal changes, trauma, and venous stasis are suggested as possible causes, the etiology is still unknown [5]. On our latest review of literature from year 2000 to 2020 using the PubMed Central search engine, 25 articles (32 cases) were retrieved ( Table 1). The most common sites of oral angiomyomas were the lip [2,4,[12][13][14][15], cheek or buccal mucosa [5,8,14,[16][17][18], palate [7,[19][20][21],   Case Reports in Dentistry tongue [6,22,23], and submandibular area [9,11,24]. The gingiva [10], mandible [2], retromolar area [2], and anterior maxillary labial fold [17] were each reported once among the studies. 73% of patients were male, and 27% were females, which is consistent with previous studies [25,26]. The mean age was 43 ± 16:57 years old (range 2 to 79). Only one study reported a congenital angiomyoma in the tongue [3]. In all reviewed studies, the patient faced a painless swelling. Only three cases reported pain associated with the lesion [7,21,24]. Preoperative radiologic assessments varied among the studies, from no radiographic assessments and plain radiography to ultrasound, MRI, and CT evaluations. To our knowledge, this is the first case report of angioleiomyoma        Smooth muscle punctuated with thick-walled venous vascular channels -9 Case Reports in Dentistry with a thorough imaging assessment including color Doppler sonography, MDCT, and MRI. The lesion was slightly heterogeneous hypoechoic mass with slight vascular flow in the color Doppler sonography; in addition, the T1-weighted and T2-weighted sequences were low and high, respectively. The high T2-weighted sequence may be seen in cysts, benign or low-grade minor salivary gland tumors, and rare hemangiomatous lesions [27]. In this case, differential diagnosis such as benign lesions of salivary gland origin was suggested in lower possibility because the lesion was located between the buccinator muscle and skin. Cystic lesions were also excluded as the sonography of the cyst is homogenous and unechoic [28]. Differential diagnosis may suggest other benign mesenchymal tumors such as fibroma, lipoma, and neurofibroma and vascular lesions including arteriovenous malformation, lymphangioma, and hemangioma. However, these lesions may have different radiographic and imaging characteristics. According to previous studies, the intraosseous angioleiomyomas are radiographically unilocular or multilocular radiolucent lesions. They can have either an ill-defined or a well-defined sclerotic border [2,11].

Case Reports in Dentistry
In this case, H&E histologic examination showed a tumor consisting of thin-and thick-walled blood vessels in a background of smooth muscle proliferation. Having numerous blood vessels may pretend other benign vascular tumors such as hemangioma, hemangiopericytoma, hemangioendothelioma, vascular malformation, and other neurovascular hamartomas [29], but a definite examination could rule out these lesions because of the smooth muscle background. Immunohistochemically markers like SMA and MSA (muscle-specific actin) can be useful in identification of smooth muscle nature of the cellular stroma [15,30,31]. In the present study, IHC staining was positive for both desmin and SMA. Various IHC stainings were carried out among studies (Table 1) although SMA and desmin were the most frequent. Depending on the apparent features of the blood vessels, IHC staining of endothelial cell markers such as CD34 and CD31 was not recommended. Other differential diagnosis histopathologically is leiomyosarcoma if there were more cellular pleomorphism and mitosis figures. In addition to well circumscribing of this tumor, lacking of anaplasia and bizarre cells, fewer than 5 mitoses per 20 high-power fields could rule out sarcoma.
In all evaluated cases, the lesion was resected with an excisional biopsy under local or general anesthesia. There are no recurrences after resection.

Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
The authors declare no conflict of interest.