Pleomorphic adenoma of the hard palate

Introduction

Pleomorphic adenoma or mixed tumor is a benign salivary gland tumor, presenting usually in the parotid or submandibular glands. This tumor contains elements of both epithelial and mesenchymal origin.[1] Rarely, may arise from the minor salivary glands localized in the hard palate and other parts of oral mucosa.[2] We report a patient suffering from a pleomorphic adenoma of the hard palate and discuss the therapeutic and diagnostic features of this condition.

Case Report

A 45-year-old female presented with a painless swelling over the palate of six months duration. There was no preceding history of trauma and her past medical history was unremarkable. The general health of the patient was preserved.

On examination there was a 1x1.5cm sized, firm, non-tender, warty, circumscribed lesion in the midline of the hard palate [Figure - 1]. It was adherent to the underlying structures and surface was covered with erythematous mucosa. There was no regional lymphadenopathy and her general physical and systemic examination was normal.

A clinical differential diagnoses of condylomata acuminata, squamous cell carcinoma, oral papilloma, minor salivary gland tumor, Kaposi′s sarcoma, syphilitic gumma, and intraoral molluscum contagiosum were considered. An incisional biopsy revealed a benign tumor having characteristic features of pleomorphic adenoma Radiograph of maxilla did not show bony invasion and serology for syphilis was negative. The entire tumor was excised with a wide margin and the underlying bone was drilled out. There has been no recurrence at six months of follow up.

Discussion

Pleomorphic adenoma, also known as benign mixed tumor is the most common tumor of salivary glands. It mostly arises in the parotid or submandibular salivary glands.[1] It may also arise in the minor salivary glands that are distributed throughout the oral cavity. The most frequent site of pleomorphic adenoma of the minor salivary glands is the hard and soft palate, followed by the upper lip.[2] The term pleomorphic describes the embryogenic basis of origin of these tumors, which contains both epithelial and mesenchymal tissues.[3] It has been postulated that these tumors arise form intercalated and myoepithelial cells.[1]

Intraoral pleomorphic adenoma appears as slowly growing, painless mass, usually in the fourth or fifth decade.[2] Pain, tenderness and ulceration are unusual. Although it is a benign tumor, it has a high recurrence rate and in a small number of cases, a benign pleomorphic adenoma may degenerate into a malignant tumor.[1],[2] Pleomorphic adenomas of the oral cavity lack a well defined fibrous capsule, a feature associated with a high recurrence rate.[2] These tumors are also able to invade and erode adjacent bone, causing radioluscent mottling on the x-ray of the maxilla.[4]

The diagnosis of pleomorphic adenoma is established on the basis of history, physical examination, cytology and histopathology. CT scan and MRI can provide information of the location, size and extension of tumor to surrounding superficial and deep structures.[5]

The tumor presents morphologically diverse features, however, both epithelial and mesenchymal elements must be present for diagnosis.1,2 Histopathology reveals a tumor composed of islands of stellate and spindle cells that are interspersed in a myxoid background.1 The pleomorphic nature is determined by an inner layer of epithelial cells and an outer layer of myoephithelial cells arranged in a variety of patterns associated with scant or abundant stroma. Variation may include squamous metaplasia, calcification, cartilage-like tissue, oxyphillic cells and rarely malignant transformation.[1],[2]

The treatment of pleomorphic adenoma of the hard palate is surgical excision with a surrounding cuff of normal tissue.[1],[2] The excision should include periosteum or bone if these are included.[2] These tumors usually do not recur after adequate surgical excision. Most recurrences can be attributable to inadequate surgical techniques such as simple enucleation leaving behind microscopic pseudopod-like extensions.[2]