Large Pleomorphic Adenoma of Hard Palate.

Pleomorphic adenoma (PA) is a benign tumor of the salivary glands commonly seen in the parotid and submandibular salivary glands. Rarely, it is seen in the minor salivary glands located at lips, palate, and other parts of the upper aerodigestive tract. We report a case of an unusually large PA of the hard palate in a female patient involving left maxillary sinus and nasal cavity. After excising, the tumor with adequate clinical margins (1 cm), a large postsurgical defect was managed by the use of obturator and it gradually healed by secondary intention in about 6-month period. The unique feature in our case was that in spite of the long duration of the tumor (30 years), it did not undergo malignant transformation.

INTRODUCTION

Salivary gland tumors constitute about 3% of all neoplasms. The majority of these tumors are benign, of which about 70% are pleomorphic adenomas (PAs). PA is a mixed tumor composed of epithelial and myoepithelial cells, demarcated from the surrounding tissue by a fibrous capsule. It represents 45%–74% of all salivary gland tumors and 65% of them occur in the parotid gland.[1] The palate, nasal cavity, and nasopharynx have abundant minor salivary glands, and PA is the most common benign tumor of these glands. The palate is the most common site of the minor salivary glands affected.

CASE REPORT

A 56-year-old female presented with a 30-year history of swelling in her mouth which was small initially and gradually increased in size. She also complained of change in voice and difficulty in swallowing. There was no history of nasal obstruction and visual defect. Intraoral examination revealed a solitary well-defined dome-shaped growth on the palate, measuring 3 cm × 4 cm in size with smooth surface [Figure 1]. Swelling extended anteriorly up to palatal aspect of maxillary central incisors, posterior extent of tumor could not be observed, and inferiorly the growth extended up to the dorsum of the tongue and laterally extended into the edentulous space with relation to 26. On palpation, swelling was firm in consistency and nontender and fixed with underlying structures.

Figure 1

Extent of tumor in oral cavity

The occlusal radiograph showed a diffuse radiolucency in relation to 25, 26, and 27 region, measuring approximately 2 cm × 1 cm in size extending up to the midline. Computed tomography (CT) scan (coronal section taken at maxillary sinus region) showed a homogenous hyperdense area present in left half of maxilla arising from the alveolar process, lifting the floor of left maxillary sinus, and also involving the left half of nasal cavity [Figure 2]. Mild postcontrast enhancement was seen. Aspiration cytology showed few myoepithelial cells with numerous polymorphonuclear neutrophils in background of red blood cells.

Figure 2

Coronal computed tomography scan showing the extent of tumor

Based on the clinical examination and investigations, a provisional diagnosis of benign salivary gland tumor was made and surgery planned. Through external approach, the tumor was excised with 1-cm clinical margins, and an acrylic obturator was placed to cover the oral defect [Figure 3]. The size of the obturator was gradually reduced according to the healing of the defect. Follow-up examination was done every month [Figures 4 and 5], and the defect completely healed at the end of 6 months. There was no recurrence after 2 years of follow-up. On gross examination, the excised tumor was pinkish, lobulated and had focally glistening cut surface. The excised tumor was sent for the histopathological examination which showed an admixture of epithelial and stromal components. Ducts lined by inner epithelial and outer myoepithelial cells were seen surrounded by a chondromyxoid stroma consistent with PA [Figure 6].

Figure 3

Postoperative obturator in situ

Figure 4

Postoperative secondary wound healing

Figure 5

Preoperative tumor bulge and postoperative scar mark

Figure 6

Photomicrograph showing admixture of epithelial and stromal components

DISCUSSION

Majority of the tumors of minor salivary glands are malignant with only 18% being benign. Of the benign tumors, PA is the most common.[2] The most common site of this tumor is the palatal area (approximately 73%),[3] followed by upper lip (17%),[4] buccal mucosa, floor of the mouth, tongue tonsil, pharynx, and retromolar area. The unusual sites are sinuses, larynx, epiglottis, and trachea. PAs have also been reported in tongue, soft palate, uvula, and even external auditory canal. Review of literature reports a few cases of PA arising in the parapharyngeal space.[5]

In the oral cavity, PA arises as a painless, slow-growing, dome-shaped firm swelling which is usually 1–2 cm in diameter. In our case, the swelling was about 3 cm × 4 cm which is an unusually large swelling. The symptoms are mainly due to mass effect of the swelling and include difficulty in mastication, swallowing, and speech. Rarely, the mucosa over the swelling ulcerates because of constant friction and results in bleeding.

Many other types of lesions can occur in the palatal region that should be considered in the differential diagnosis. These include maxillary fibromyxoma, ameloblastoma, adenoid cystic carcinoma, adenocarcinoma, and myoepithelioma. CT scan is the important diagnostic tool of these tumors; it helps to determine the extension of the lesion.[6] Cytological findings in PA are typical of mixed epithelial cells and mesenchymal elements. Histopathological examination confirms the diagnosis.

Surgical excision is the treatment of choice. The primary goal of excision should be complete excision of the tumor with at least 1-cm clinical margin to avoid any chances of recurrence. Deciding the approach for reconstruction of defect depends on functional and esthetic requirements of the patient. Although soft-tissue defects of the hard palate can be left to granulate, the bony defects in dentate can be treated with obturator or free tissue transfer techniques to augment the anterior projection of the face. Soft tissue can be used to seal the oral cavity from the nose. This technique is particularly helpful in bony defects of the upper alveolar ridge, which causes significant cosmetic and functional deformity. The oroantral communication that comes into existence after the dissection of the tumor can be supplied with plastic surgery by the Wassmund–Borusiewicz method.[7] In our case, obturator was used to cover the oroantral communication, which later healed by the secondary intention. Longevity and recurrence are risk factors for malignant transformation. The propensity for malignant transformation is documented to be 1.9%–23.3%.[8] In spite of a long duration (30 years), the tumor in our case did not undergo malignant transformation.

CONCLUSION

Although a common entity, PA can be a challenging tumor to diagnose when it is present in the oral cavity. Its histological diversity makes it a unique tumor. A multidisciplinary approach involving pathologist, radiologist, and surgeon is required to effectively manage the tumor. Although rare, recurrence, and malignant transformation should be kept in mind while excising the tumor. The goal of maintaining speech, swallowing, and anterior facial projection should be kept at the forefront of each surgeon's mind while approaching these difficult cases.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.