A Benign Intraoral Swelling – Case Report

INTRODUCTION

Salivary glands arediverse group of anatomic structures. A variety of pathologies arises from salivary glands. The major salivary glands are three in number namely parotid, submandibular and sublingual glands, whereas the minor salivary glands are distributed alonglips, buccal mucosa, labial mucosa, lingual mucosa, soft and hard palate, and floor of mouth. Pathologies involving the minor salivary glands are rare compared to the major salivary glands. The palate is the most common intra oral site accounting for 60% of the neoplastic changes.

Swellings in the palate may result from a variety of etiological factors.The most common swellings in the anterior palate are the odontogenic abscess, cysts, and tumors. The management of these pathologies requires a thorough clinical and radiographic examination correlated with the histopathology.^1,2 This report is an unusual occurrence of a benign salivary gland tumor in a 35 year old female .

CASE REPORT

A 35 year old female patient reported to the Department Of Oral Medicine And Radiology, Rajarajeswari Dental College and Hospital, Bangalore, India, with a swelling on the palate. The patient was conscious about the swelling since three weeks although it was asymptomatic. The patient had a history of extraction of left and right upper back tooth an year before and a two unit fixed prosthesis was placed on the upper right tooth region. The medical and personal history of the patient were noncontributory. No gross facial asymmetry was noted. The mouth opening and temporomandibular joint were normal. No palpable lymph nodes were detected.

On intra oral examination, a solitary ovoid swelling approximately 2cmx3cm was present on the anterior part of hard palate.(Fig 2).

The lesion was extending medio-laterally (1.5cm) and antero-posteriorly (2cm) in relation to 14 and 15 region. The mucosa over the swelling appeared normal with smooth and rounded margins. No visible pulsations were observed. All inspectory findings were confirmed. The swelling was soft in consistency, nontender on palpation and neither compressible nor reducible. There was no expansion of cortical plates.

Other hard tissue findings were generalized gingival recession, missing teeth in relation to 14 24 35 36 37 45 46 47, a fixed prosthesis in relation to 15 16, and sub gingival calculus with extrinsic stains. No vestibular tenderness was palpated. The fixed prosthesis was non tender on percussion.

Based on these findings, a provisional diagnosis of benign salivary gland tumor of minor salivary gland was reached and differential diagnosis of palatal abcess, retention mucocele and pleomorphic adenoma were considered.

Intraoral periapical radiograph of 14, 15 16, and maxillary cross sectional occlusal radiographs were taken. (Fig 3, Fig 4). There was missing tooth in relation to 14 and 16. The prosthetic crown was in relation to 15 16 17. No pathological changes were evident. The patient underwent routine hematological investigations. The routine blood investigations showed normal parameters for all tests. Fine needle aspiration cytology revealed blood filled fluid. A complete excisional biopsy was performed under local anesthesia followed by placing a surgical palatal plate. (Fig 5, Fig 6). Histopathological examination revealed encapsulated lesional tissue, composed of small, round darkly stained tumor cells which is highly cellular and arranged in sheets. Focal areas also showed ductal arrangement with eosinophilic coagulam suggestive of pleomorphic adenoma.A two month follow up was done which showed a satisfactory healing. The patient was referred to the Department of Prosthodontics for prosthetic rehabilitation of the missing tooth.

DISCUSSION

Pleomorphic Adenoma (PA) is defined by world health organization in 1972 as a circumscribed tumor characterized by its pleomorphic or mixed appearance clearly recognizable epithelial tissue being intermingled with tissue of mucoid, myxoid and chondroid appearance. Willis coined the term ‘Pleomorphic Adenoma’. The other names are Enclavoma, Endothelioma, Branchioma, Enchondroma. It is the most common major salivary gland tumor. Tumors of minor salivary glands are rare and contributes to 4-6% of all the salivary gland tumors.^2,3,4,5 The present case is one such rare form of neoplasm of minor salivary gland of the palate. 84% of the PA’s arises from parotid gland, 8% in the submandibular gland, 4-6% in the minor salivary gland, among which the common site of occurrence is the palate, followed by lips and buccal mucosa. The mixed minor salivary tumors is more prevalent in elderly women.

The exact etiology of pleomorphic adenoma is unclear. However, there are many contributing factors like smoking, ionizing radiation, chromosomal abnormalities, viral infections, occupational hazards and endogenous hormonal disturbances.6In the present case however, the etiology is unclear.

The embryological basis of PA is their origin from intercalated and myoepithelial cells arranged in variant morphological patterns. It has more predilection for females of 3rd to 5th decade of life. Our case was also about a 35 year old female patient. More commonly seen unilaterally, it presents as slow growing painless swelling with smooth and rounded margins unless secondarily ulcerated. Due to the resiliency of the palatal mucosa the swelling appears to be fixed unlike other locations.^3-6. Likewise in the present case the palatal swelling was ovoid in shape with smooth margins and non pinchable mucosa.

In our case, palatal abcess was considered as differential diagnosis as it is a common palatal swelling of odontogenic origin. It appears as a fluctuant mass most commonly lateral to the premolar region of the hard palate. Moreover, the patient hada prosthetic crown in relation to 15 and 16 on clinical examination along with gingival recession which was asymptomatic. As the IOPAR in relation to 14 15 16 showed missing tooth in relation to 14 and 16 and no periapical changes in relation to 15, palatal abcess was ruled out.

The retention mucocele is common in the age group of 15-35 years with slight female predilection. It appears as firm asymptomatic swellings ranging in size from few millimeters to several centimeters. The study done by CB Moore et al shows that the prevalence of retention mucocele is around 15.52% with upper lip and hard palate being the common sites of occurrence.⁷ However the final diagnosis depends on histopathological examination.^7,8

Multiple imaging modalities are available for visualizing the radiographic changes of PA. In minor salivary gland tumors , especially involving the palate , maxillary occlusal is the radiograph of choice for screening the extent and osseous involvement of the lesion. In our case the occlusal radiograph was satisfactory as the size of the lesion was small and no evidence of bony involvement were seen. However, for very severe lesion.

Higher imaging modalities like the choice of MRI stands more than CT as it shows excellent soft tissue resolution on the basis of signal intensity characteristics.

Being well known for the histopathological appearance, PA derives the name from the architectural pleomorphism visible on light microscopy. PA also known as mixed tumorsalivary gland type, describes the pleomorphic appearance as opposed to its dual origin from epithelial and myoepithelial elements. Histologically, four subtypes are present based on the cellularity namely Type I (myxoid), Type II (myxoid and cellular), Type III (predominantly cellular), Type IV (extremely cellular). Types I and II stains homogenously whereas, types II and IV stains heterogenously.

In the present case, encapsulated lesional tissue, composed of small, round darkly stained tumor cells which is highly cellular and arranged in sheets along with focal areas of ductal arrangement was seen.^9,10 Our case belongs to more of type IV histological variant of pleomorphic adenoma.

The commonly employed treatment modality is the complete surgical excision of the lesion with wide and negative margins. As the tumor is well encapsulated, the chances of recurrence are higher if the lesion is resected incompletely. In the present case also, excision under local anesthesia was done.

The choice of radiation therapy is contraindicated, as the lesion is radio resistant. The recurrence of PA is attributed to the islands of tumor tissue left behind after the surgery, and the multicentric nature of PA. Therefore, long-term follow-up is recommended.

Malignant potential of Pleomorphic Adenoma ranges from 1 to 10% with an increased risk for longstanding lesions. Malignancy must be suspected with the presence of clinical features such as pain, ulceration, fixity, spontaneous bleeding.^11,12

CONCLUSION

Pleomorphic adenoma is common tumor of major salivary gland, whereas, the tumor involving minor salivary gland is rare. The lesion involving minor salivary gland has a variety of clinical presentations. However, the presentation varies according to the degree of pain, enlargement, loss of elasticity, and surface changes. Some patients report periods of relative quiescence interrupted by transient or persistent painful episodes whereas others preset with asymptomatic swelling irrespective of the chronicity of the lesion. Definitive diagnosis lies in the histopathological examination, and the management is the surgical excision of the lesion with wide margins. Considering these aspects makes this case a rare entity. Excellent results are seen if the wound is allowed to granulate and heal by itself. Recurrence of the lesion is minimal, however long term follow up is required for better prognosis.