Oral angioleiomyoma : a case report and considerations on differential diagnosis

First submission on 11/04/13; last submission on 09/08/13; accepted for publication on 11/08/13; published on 20/12/13 1. PhD in Oral Pathology; associate professor, Postgraduate Program in Oral Pathology, Universidade Federal do Rio Grande do Norte (UFRN), Brazil. 2. MSc in Dentistry; PhD candidate-Postgraduate Program in Oral Pathology, UFRN, Brazil. 3. PhD in Stomatology-Oral and Maxillofacial Surgeon, Hospital Regional do Agreste, Brazil. 4. PhD in Dentistry; professor and Head, Caruaru Dental School, Brazil. ABStrACt


introDuCtion
Leiomyomas are benign mesenchymal tumors derived from smooth muscle, which most often occur in the uterus and gastrointestinal tract.According to the World Health Organization (5) , leiomyomas are divided into two categories: angioleiomyoma and leiomyoma of deep soft tissue.Angioleiomyomas are solitary forms of leiomyomas that usually occur in the subcutis and are the most common variant of leiomyomas affecting the oral cavity (12) .
From a clinical point of view, angioleiomyomas are usually superficial, well-circumscribed and asymptomatic small lesions with slow growth, covered by normal mucosa, and sometimes bluish or purple in color (7,9) .The most common oral sites for angioleiomyomas are the lips (27.46%), followed by the tongue (18.30%), cheeks and palate (15.49%), gingiva (8.45%), and mandible (5.63%) (2) .The greatest incidence is in the 40-59year age group (4,15) .We report a case of an angioleiomyoma occurring in the maxillary gingiva with clinical characteristics of a peripheral giant cell granuloma.

CASE rEPort
A 43-year-old man was referred to the Department of Stomatology of the Caruaru School of Dentistry for diagnosis and treatment of an exophytic asymptomatic lesion of the upper gingiva.The lesion appeared red-to-violet in color with a lobulated surface and arose in the gingiva between the maxillary right cuspid and the left central incisor from a sessile base (Figure 1).The lesion was painless, measured approximately 1.5 × 1 cm in diameter, fibrous in consistency, and firm upon palpation.
The lesion had been first noticed by the patient 6 months earlier after a tooth extraction, and it had grown slowly to its present size.The patient's oral hygiene was poor.Furthermore, generalized periodontitis and advanced attrition were diagnosed.The medical history was essentially noncontributory and the patient was taking no medications.A periapical radiograph revealed a well-defined radiolucent area between the 11 and the 23, suggesting mild osseous erosion consistent with cupping of the underling bone (Figure 2).The clinical differential diagnosis included a peripheral giant cell granuloma and a benign mesenchymal neoplasm.Surgical excision of the lesion was performed, and moderate bleeding was noted and controlled with pressure on the area.
Microscopic examination showed a tumor mass encapsulated by a fibrous tissue of varying texture and thickness, and covered by a normal keratinizing stratified squamous epithelium.The lesion was composed of large vascular channels of varying caliber, surrounded by thick walls of irregularly arranged, spindle-shaped cells (Figure 3A).The tumor cells were large, with indistinct cell margins, scant and faintly eosinophilic cytoplasm as well as elongated nuclei with rounded edges (Figure 3B).Whorled bundles of muscle fibers were sometimes fused with the vessel walls.Positive immunostaining for smooth-muscle actin and desmin were observed in the tumor cells (Figures 3C and E), whereas CD-34 was positive in the endothelium (Figure 3D).S-100 staining was negative in the tumor cells (Figure 3F).A diagnosis of angioleiomyoma was established.No complications were observed after a one-month follow-up (Figure 4) and there was no recurrence after a 14-month follow-up.

figurE 3 -Microscopic features of the angioleiomyoma A: smooth muscle proliferation around slit-like endothelium-lined vascular spaces (hematoxylin-eosin; original magnification 100×); B: large tumor cells with indistinct cell margins and faintly eosinophilic cytoplasm, showing elongated nuclei with rounded edges (hematoxylin-eosin; original magnification 200×); C: immunostaining for smoothmuscle actin showing strong positivity in the proliferating spindle-shaped cells, which form thick vessel walls (streptavidin-biotin technique; original magnification 100×); D: CD34 immunoreactivity is observed in the endothelial cells, demonstrating the high grade of vascularization of the lesion (streptavidin-biotin technique; original magnification 100×); E: neoplastic cells with positive immunostaining for desmin (streptavidin-biotin technique; original magnification 100×); F: neoplastic cells negative for S-100 (streptavidin-biotin technique; original magnification 100×).
Oral angioleiomyoma: a case report and considerations on differential diagnosis

DiSCuSSion
Angioleiomyomas are rare tumors in the oral cavity, representing only 0.016% to 0.065% of all leiomyomas (3,8,16) , due to the paucity of smooth muscle in this region.Most authors agree that the tumor arises from the tunica media of small vessels, but other sources have been suggested, such as the smooth muscle of the circumvallate papilla of the tongue, arteriovenous anastomoses, and from ectopic smooth muscle associated with aberrant hair follicles, particularly in the cheek (1,7,12,13,15) .We believe that the gingival angioleiomyoma probably originated from the smooth muscle of blood vessels.
When found in the oral mucosa, angioleiomyomas most commonly affect the lips, followed by the tongue, cheeks, and palate (2) .Angioleiomyomas of the gingiva are very rare, accounting for only 0.9% of the oral angioleiomyomas reported in the English literature (3) .In the current case, a peripheral giant cell granuloma was most strongly suspected preoperatively because of the location, color, absence of symptoms, and progression of the lesion.
Histologically, we found a lesion composed of spindle-shaped cells presenting elongated nuclei with rounded ends, which were closely compacted with a fibrous stroma surrounding large vascular channels.These findings corroborated the reports in the literature regarding the typical microscopic appearance of an angioleiomyoma, which is a well-defined nodule of smooth muscle tissue punctuated with thick-walled vessels with a partially patent lumen (1,3,6,13,(17)(18)(19) .Typically, the inner layers of smooth muscle of the vessels are arranged in an orderly circumferential fashion, whereas the outer layers spin or swirl away from the vessel, merging within the less well-ordered peripheral muscle fibers (19) .
In the present case, the tumor cells were positive for smooth muscle actin (SMA) and desmin, whereas the endothelium exhibited immunoreactivity for CD-34.S-100 protein was not identified in the tumor cells.Monoclonal antibody to SMA reacts with the muscle cells of vessels and it is useful for excluding a diagnosis of schwannoma, fibromatosis, fibrosarcoma, and malignant schwannoma since those tumor cells are negative for SMA.Hemangiopericytomas and hemangioendotheliomas are also negative for SMA inasmuch as these lesions do not have a smooth muscle component in their vessel walls (17) , although their endothelium is generally positive for CD-34.This antibody is useful to define the degree of vascularization of the lesion.
Myopericytomas show histological and immunohistochemical overlap with angioleiomyomas, including SMA expression.However, only angioleiomyomas coexpress SMA and desmin, which reflects an advanced smooth muscle differentiation (10) .Leiomyoblasts are negative for S-100 (13) and CD-34 antibodies.On the other hand, tumor cells of schwannomas, neurofibromas, and malignant schwannomas usually show strong staining for S-100 (19) .The number of mitotic figures, anaplasia, and bizarre cell forms are regarded as features that may aid in the distinction between leiomyomas and low-grade leiomyosarcomas (15) .