Gingival angioleiomyoma-infrequent lesion of oral cavity at a rare site.

Gingival angioleiomyoma are rarely encountered lesions and most of these lesions are excised in toto in view of reactive gingival epulitic lesions. However, due to the vascular nature of these lesions, many a times surgeons experience unexpected hemorrhage and require extensive hemostatic management. A preoperative diagnosis is a must for these lesions and at least color imaging techniques can be utilized to know its vascular nature and preoperative tumor embolization can be done to be on the safer side. Also histopathological dilemma can occur due to the varied types of vascular arrangement in angioleiomyoma or due to simulation of other vascular lesion like hemangiomas, as well as due to similarity with other spindle cell neoplasms. We advocate the use of immunohistochemistry (IHC) to establish the exact diagnosis in such cases. Also due to infrequent reports of angioleiomyoma in such unusual location, we want to record this case for further reference in future.

INTRODUCTION

Leiomyoma, a benign smooth muscle neoplasm is classified by World Health Organization on the basis of histopathology into three types: 1) solid, 2) vascular (angiomyoma, angioleiomyoma) and 3) epithelioid. Leiomyoma is a common neoplasm of uterus and gastrointestinal tract mostly occurring in solid variant.[12] In the head and neck region, leiomyoma is rare and in oral cavity, it accounts for only 0.4% of all soft tissue neoplasms and 0.06% of all leiomyomas. Oral leiomyoma mostly presents as angioleiomyoma variant accounting for 64–66.2% of all reported cases.[3] It has a wide range of age presentation and no definite gender predilection.[4] Common site of occurrence in oral cavity is lip, tongue, cheek and palate. Less commonly it can involve gingiva, mandible and other mucosal sites.[1] Usually, it is slow growing, asymptomatic, firm nodular mass and occasionally painful. Angioleiomyoma exhibits blue or red discoloration.[4] We report a rare case of large mandibular gingival angioleiomyoma showing predominantly cavernous-type histopathological growth pattern.

CASE REPORT

A female patient of 45 years of age reported to a private oral and maxillofacial surgeon with a huge sessile soft tissue mass measuring about 3 × 3 cm diameter, with an erythematous hue and associated tooth displacement in lower left mandibular posterior gingiva. The lesion occupied the whole left buccal vestibular space leading to extraoral left side midfacial enlargement [Figure 1]. History revealed a slow enlarging painless mass of two and half year duration. Panoramic radiograph revealed only erosion of underlying bone and no definite osseous component along with displacement of associated premolars and molars [Figure 2]. A presumptive diagnosis of pyogenic granuloma due to its clinical appearance was made and surgical excision was done. Massive bleeding was encountered during excision and was controlled using multiple ligation, cautery and packs. Grossly, a soft tissue nodular mass of approximately 3 × 3 cm, firm in consistency with grayish-white appearance and two associated mandibular premolars were submitted [Figure 3]. Multiple small tissues were cut and processed for routine histopathological examination.

Figure 1

Soft tissue gingival mass in lower left posterior region occupying vestibular space as well as lingual sulcus

Figure 2

Orthopantomogram reveals no underlying bony origin and displacement of premolar and molars along with bony resorption on left mandibular jaw

Figure 3

Excised gross specimen along with extracted teeth.

The hematoxylin and eosin-stained section showed multiple small to large dilated vascular channels with some of them showing thick vascular wall. Inter-vascular areas showed spindle cells with eosinophilic cytoplasm and elongated blunt-ended cigar-shaped nuclei with perinuclear vacuole. These spindle cells seemed to merge with the vascular wall. Many vessels showed thin-dilated wall and myxoid inter-vascular stroma [Figure 4a–d]. A diagnosis of angioleiomyoma was given and immunohistochemistry (IHC) for smooth muscle actin (SMA) showed diffuse intense positivity in vascular wall and intervascular stroma confirming their smooth muscle nature [Figures 5 and 6]. Patient is on follow up and is free of recurrence after a year.

Figure 4

(a) Surface epithelium with underlying connective tissue showing variably sized vessels in eosinophilic spindle cell stromal population (H&E stain, ×40). (b) Large thick-walled vessels associated with intersecting fascicles of spindle shaped smooth muscle cells (H&E stain, ×100). (c) Thick vessel wall composed of smooth muscle cells mingling with intervascular stroma (H&E stain, ×100). (d) Spindle smooth muscle cells with eosinophilic cytoplasm and cigar-shaped bluntended nuclei with perinuclear vacuole (H&E stain, ×400)

Figure 5

IHC for SMA shows diffuse positivity in tumor stroma (IHC stain, ×100)

Figure 6

Intense cytoplasmic SMA staining of tumor smooth muscle cells (IHC stain, ×400)

DISCUSSION

Oral leiomyoma is rare due to paucity of smooth muscles in this region and whatever is found is associated with blood vessels (tunica media), circumvallate papillae (ductus lingualis) and heterotopic smooth muscle. Angioleiomyoma is the most common variant encountered in oral cavity followed by solid and rarely by epithelioid variant of leiomyoma.[1] Few cases of oral granular cell leiomyoma have been reported.[5] Angioleiomyoma mostly involves lower lip, tongue and palate followed by other rare mucosal sites. Gingiva is a rare location and few cases have been reported (less than 20 cases) in literature.[6] Trauma, topical estrogen, hormonal imbalance, infection, arteriovenous malformation, venous stasis and genetic translocation have been implicated as etiology but without any clarity.[235] A wide age range of patient involvement has been reported without definite gender predilection.[4] Oral angioleiomyoma typically presents as slow growing, firm, sessile and nodular soft tissue mass of 5 mm to 2 cm size. A few of the cases larger than these have also been reported. Bluish or reddish discoloration with rare history of pain have been reported, but cases associated with extremities are mostly painful.[34]

Term angioleiomyoma was coined by Stout in 1937 and is circumscribed with distinct eosinophilic spindle cells with blunt-ended cigar-shaped nuclei and perinuclear vacuoles arranged in intersecting fascicles at right angle with abundant vascular channels having varying patterns.[478] According to the predominant vascular pattern angioleiomyoma is classified into three variants, namely:- 1) solid (capillary) angioleiomyoma composed of narrow, slit-like vascular channels with surrounding densely packed intersecting smooth muscle fascicles. 2) Venous angioleiomyoma composed of thick vessels and smooth muscle of vessel wall blending with intervascular smooth muscle bundles giving a net-like appearance to vessel wall. 3) Cavernous angioleiomyoma has dilated vascular channels with sparse smooth muscle and muscular wall of these vessels are difficult to distinguish from intervascular smooth muscle bundles.[8910] The efficacy of imaging system is restricted to know the nature and extent of lesion only. The definite diagnosis can be given by histopathological examination.[2] Ultrasound or color flow imaging reveals the tumor as a vascular lesion, so massive bleeding during excision is always a possibility. To be on safer approach, preoperative embolization of tumor can be done to potentially reduce bleeding during excision. So the treatment of choice is surgical excision along tumor margins or capsule. Recurrence is rare if excised completely.[3] Malignant transformation is rare and follow up should be done periodically as a case of leiomyosarcoma shows areas of angioleiomyoma.[11]

Histopathologically, angioleiomyoma can mimic cellular benign fibrous histiocytoma, myofibroma and leiomyosarcoma and closely it mimics angioleiomyoma-like myopericytoma.[12] Cellular benign fibrous histiocytoma shows less eosinophilic spindle cells arranged in mostly fascicular pattern or less commonly storiform pattern admixed with histiocytoid cells and is only positive for vimentin. Myofibroma shows overlapping similarity with leiomyoma, at periphery it shows positivity for SMA and desmin negativity but central zone shows primitive appearing round cells arranged about hemangiopericytoma component with SMA negativity.[4]

Myopericytoma is characterized by round to oval cells with eosinophilic cytoplasm arranged circumferentially in layers around vascular lumina.[13] Angioleiomyoma usually lacks this characteristic perivascular concentric growth of myoid tumor cells. However, Matsuyama et al., has compared angioleiomyoma and myopericytoma on immunohistochemical basis and suggested both to be closely related tumors.[8] However, Watanabe et al., has suggested H-caldesmon to be specific for smooth muscle cell and tumors originating from it. He showed consistent expression of H-caldesmon in normal visceral and vascular smooth muscle cells and also myoepithelial cells but not in myofibroblasts and vascular pericytes.[14]

CONCLUSION

Gingiva is prone for many reactive lesions as well as benign lesions. The most commonly encountered are especially seen in young female patients and include pyogenic granuloma, peripheral giant cell granuloma, peripheral ossifying fibroma, traumatic fibroma etc. Angioleiomyoma of gingival locations is rare and seldom included in differential diagnosis. Clinically it mimics vascular lesions like pyogenic granuloma, peripheral giant cell granuloma and hemangiomas. Owing to vascular nature, a preoperative diagnosis should be confirmed by incisional biopsies, although most of small lesions are excised completely and submitted for histopathological examination. Further, it should be differentiated from other spindle cell lesions by appropriate IHC. Recent definite marker for smooth muscle H-caldesmon can be used as a specific marker for smooth muscle tumors and also can be used to differentiate among angioleiomyoma and myopericytoma.