Pleomorphic adenoma . It is the most frequent benign tumor of the salivary and parotid glands. Its name derives from the pleomorphism in its constitution, that is, its greatly variable appearance, when viewed under a light microscope. It is also known as a mixed salivary gland tumor, describing its pleomorphic characteristic instead of its origin, which is both epithelial and myoepithelial.
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- 1 Epidemiology
- 2 Clinical picture
- 3 Histology
- 4 Treatment
- 5 See also
- 6 Sources
According to the classification of the World Health Organization , published in 1991 , there are more than 30 histological varieties of neoplasms of the parotid gland . Pleomorphic parotid gland adenoma is the most common type of benign salivary tumor, about 80% of all cases of salivary tumors. Tends to be more prevalent in white people than in other races, women are affected predominantly over men in a ratio close to 3: 2 and typically occur between the fourth and sixth decade of life — average patient age is approximately 43 years being very rare to find these tumors in children.
Pleomorphic adenoma is a usually solitary tumor and presents as a firm, slow-growing, painless, nodular mass 85% of the time from one of the parotid glands and the rest in the submandibular, lingual, and salivary glands. Isolated nodules are usually single node growths, rather than multinodular presentation, and rarely present as tumors in both parotids at the same time.
They are usually mobile unless they are located on the palate and can cause atrophy of the jaw when located in the parotid gland. If they are found in the tail of the parotid, eversion of the ear lobe may occur. Although classified as benign tumors , pleomorphic adenomas have the ability to grow to very large proportions and have the ability to eventually transform into malignant carcinoma, a risk that increases over time. It may also recur after being removed, may invade adjacent normal tissue, and metastasize to other distant tissues, especially over time intervals greater than 10 years.
Under the microscope, they have a highly variable appearance, even within the same tumor. Classically, it is a biphasic tumor and is characterized by having a mixture of polygonal epithelium and spindle-shaped myoepithelial elements against a highly variable stromal background that can be mucoid, myxoid, cartilaginous, or hyaline. Epithelial elements can be arranged in the form of structures ductal, either in laminar form, grouped or in interlocking filaments. The cells that make up the epithelium are of two types, luminal (epithelial) and non-luminal (mesenchymal) and can also be polygonal, laminar or stellate (hence the term pleomorphic). Areas of squamous metaplasia and epithelial pearls may be present.
The tumor is not enveloped, but is usually surrounded by a pseudo-capsule of varying thickness. The tumor spreads in its dimensions at variable speeds, entering the normal glandular parenchyma, forming a finger-shaped front, although this variation does not imply a malignant transformation. Often, tumor cells demonstrate a characteristic translocation between chromosomes # 3 and # 8. This causes the PLAG gene to be juxtaposed on the β-catenin gene. This activates the passage of catenin , which leads to inadequate cell division.
It is recommended that the diagnosis be confirmed by biopsy. Treatment is achieved by extensive surgical excision with a wide margin of healthy tissue to decrease the possibility of local recurrence of the disorder. Resections of this type are accompanied by rare recurrences, which occur when the tumor is treated very conservatively, that is, the Enucleation of the main portion of the tumor mass leaves microscopic foci of tumor cells in the surrounding area that regrow in the form of a recurrent tumor or carcinoma.
These are operations with a large list of sequels, including nerve damage, Freys syndrome, cosmetic problems, etc.