Clinical Presentation
The pleomorphic adenoma is a benign yet true neoplasm. It will continue to grow, or regrow if not completely excised, but it is incapable of metastasis. Seventy-five percent of tumors that occur in the parotid gland in adults are pleomorphic adenomas and 5% are Warthin tumors. Pleomorphic adenomas account for 45% of all oral minor salivary gland tumors. When they arise in the oral mucosa, the site of predilection is the mucosa over the posterior hard palate and anterior soft palate
The two most common clinical presentations are a painless, firm mass in the superficial lobe of the parotid gland and a painless, firm mass in the posterior palatal mucosa.
Eighty percent of all pleomorphic adenomas in the parotid gland develop in the superficial lobe. It presents as a freely movable, firm mass. Rarely, the case fluctuate in size or be painful. It does not induce facial nerve paresis.
When a pleomorphic adenoma presents in the mucosa of the hard palate-soft palate junction, it will be a firm, painless mass with intact overlying mucosa. If the mucosa is ulcerated and the ulceration is not attributable to trauma or biopsy, the mass should be considered a malignancy. In the palatal mucosa, the mass will seem to be fixed to the palate. Because the pleomorphic adenoma cannot invade bone, this is not caused by bony invasion but rather by the inelasticity of the palatal mucosa, which becomes distended by the tumor mass and may eventuate in a cupped-out resorption of bone
Incidence
Pleomorphic adenomas can arise at any age but are somewhat more common between the ages of 30 and 50
years and are slightly more common in women.
Differential Diagnosis
The differential diagnosis of a firm mass in the parotid gland must include a Warthin tumor, which is particularly likely in men, and basal cell adenoma, which preferentially develops in the parotid gland. In addition, malignant
salivary gland tumors that must be considered include mucoepidermoid, adenoid cystic, and acinic cell carcinomas. Non-salivary gland neoplasms that are known to occur in the parotid gland—ie, hemangiomas,
lymphangiomas, lipomas, and lymphomas within parotid lymph nodes—may also present in a similar fashion.
The differential diagnosis of a firm mass in the palatal mucosa with intact overlying epithelium is primarily a
subset of other salivary gland neoplasms. In order of statistical likelihood, they are adenoid cystic carcinoma,
mucoepidermoid carcinoma, and polymorphous low-grade adenocarcinoma. Another benign tumor that requires
some consideration is the canalicular adenoma. In addition, several non-salivary gland tumors may present
with a similar appearance, such as non-Hodgkin lymphoma and neurofibroma
Treatment
For a mass in the parotid gland, the specific location in the superficial lobe is to be noted. This should be followed by a superficial parotidectomy, which represents both the diagnostic biopsy and the definitive treatment. In such a presentation, an incisional parotid biopsy would be contraindicated because throughout the biopsy site is a concern.
If a pleomorphic adenoma is confirmed, it is excised with 1-cm clinical margins at its periphery and includes the
overlying surface epithelium and the periosteum of the palate. Excision or scraping of the
palatal bone is not required because the periosteum is an effective anatomical barrier and pleomorphic adenomas do not invade bone.
