Pleomorphic Adenoma | Salivary gland tumor
The pleomorphic adenoma is the prototypical benign yet true neoplasm; that is, it will continue to grow—or regrow if not completely removed—but it is incapable of metastasis, and originates from ductal and myoepithelial elements.
It occurs at different statistical incidences in all salivary glands. Seventy-five percent of tumors that occur in the parotid gland
in adults are pleomorphic adenomas and 5% are Warthin tumors. The remaining 20% is comprised of malignant tumors and a very small number of other benign tumors (basal cell adenoma, fibromas, etc). Pleomorphic adenomas, and salivary gland
tumors in general, are not commonly found in the submandibular and sublingual glands. Nevertheless, they account for about 20% to 30% of all tumors in these glands. Oral pleomorphic adenomas are somewhat common, accounting for about 45% of all oral minor salivary gland
- Age: Pleomorphic adenomas can arise at any age but are somewhat more common between the ages of 30 and 50 years
- Sex: slightly more common in women
- Site: The site of predilection is the mucosa over the posterior hard palate and anterior soft palate is the most common intraoral site, followed by the upper lip and buccal mucosa; otherwise, pleomorphic adenomas can occur in any location where minor salivary glands exist.
- Pleomorphic adenoma in the minor salivary glands presents as an asymptomatic, slow-growing, firm swelling, 2–3 cm in size
- 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
- The tumor is usually covered by normal epithelium.
- In the palatal mucosa, the mass will seem to be fixed to the palate.
- In other oral mucosal sites, the pleomorphic adenoma presents as a freely movable, circumscribed mass.
- Pleomorphic adenomas do not induce facial nerve paresis
- Histopathological examination
- For a mass in the submandibular or parotid gland, a computed tomography (CT) scan or magnetic resonance imaging (MRI) scan is valuable to confirm its location in the respective gland
- For a mass in the palatal mucosa, a CT scan, particularly coronal views, also is recommended to determine its extent and the degree of any resorption of the palate
Important histological features of pleomorphic adenomas
- Capsule — never complete
- Sheets or strands of dark-staining epithelial cells
- Squamous metaplasia and foci of keratin
- Fibrous and elastic tissue
- Myxoid tissue
- Cartilage, sometimes calcified. Rarely, true bone formation
- Other benign and malignant salivary gland tumors
- necrotizing sialadenometaplasia
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 elaborate receptor
activator of nuclear factor κB ligand (RANKL) or other osteoclast-activating factors to invade bone. If the tumor extends to the area of the soft palate, the excision includes the fascia over the soft palate musculature. The muscles
of the soft palate need not be excised unless frozen sections indicate tumor at this margin.
For pleomorphic adenomas in other mucosal sites, a peripheral excision with 1-cm margins is recommended. This will include overlying mucosa but should not include overlying skin
if the mass is located in the lip or buccal mucosa. In these instances, the muscle fascia of the orbicularis oris or buccinator is an effective anatomical barrier.
In any site, enucleation, or a “shelling out”
of a pleomorphic adenoma, is contraindicated. The pseudocapsule of a pleomorphic adenoma will certainly give the clinical impression
of a complete removal of an “encapsulated nodule or mass” with these approaches, but the extracapsular tumor projections left behind may lead not just to recurrence but to multicentric recurrences caused by the remaining tumor projections and foci within the tissue at the circumference of the resections.
For a mass in the submandibular or sublingual gland
, complete excision of the gland
also represents a diagnostic biopsy as well as definitive treatment
Category: Dental, Oral Pathology, Oral Surgery