Pleomorphic adenoma | |
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Other names | Benign mixed tumor [1] |
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Cytopathology of pleomorphic adenoma (Pap stain). It can usually be diagnosed by its typical fibrillary stroma (mesenchyme). Stromal cell nuclei are small. Myoepithelial cells are usually the predominant cell type, and their nuclei can have various shapes but are usually more elongated than in epithelial cells. Epithelial cell nuclei may have prominent nucleoli. [2] | |
Specialty | Oncology ![]() |
Pleomorphic adenoma (or benign mixed tumor) is a common benign salivary gland neoplasm characterised by neoplastic proliferation of epithelial (ductal) cells along with myoepithelial components, having a malignant potentiality. It is the most common type of salivary gland tumor and the most common tumor of the parotid gland. It derives its name from the architectural Pleomorphism (variable appearance) seen by light microscopy. It is also known as "Mixed tumor, salivary gland type", which refers to its dual origin from epithelial and myoepithelial elements as opposed to its pleomorphic appearance.
The tumor is usually solitary and presents as a slow growing, painless, firm single nodular mass. Isolated nodules are generally outgrowths of the main nodule rather than a multinodular presentation. It is usually mobile unless found in the palate and can cause atrophy of the mandibular ramus when located in the parotid gland. When found in the parotid tail, it may present as an eversion of the ear lobe. Though it is classified as a benign tumor, pleomorphic adenomas have the capacity to grow to large proportions and may undergo malignant transformation, to form carcinoma ex-pleomorphic adenoma, a risk that increases with time (9.5% chance to convert into malignancy in 15 years). Although it is "benign", the tumor is aneuploid, it can recur after resection, it invades normal adjacent tissue, and distant metastases have been reported after long (+10 years) time intervals. This tumour most often presents in the lower pole of the superficial lobe of the gland, about 10% of the tumours arise in the deeper portions of the gland. It occurs more frequently in females than in males, the ratio approximating 6:4. The majority of the lesion are found in patients in the fourth to sixth decades with an average age of occurrences of about 43 years, but these are relatively common in young adults and have been known to occur in children.
Morphological diversity is the most characteristic feature of this neoplasm. Histologically, it is highly variable in appearance, even within individual tumors. Classically it is biphasic and is characterized by an admixture of polygonal epithelial and spindle-shaped myoepithelial elements in a variable background stroma that may be mucoid, myxoid, cartilaginous or hyaline. Epithelial elements may be arranged in duct-like structures, sheets, clumps and/or interlacing strands and consist of polygonal, spindle or stellate-shaped cells (hence pleiomorphism). Areas of squamous metaplasia and epithelial pearls may be present. The tumor is not enveloped, but it is surrounded by a fibrous pseudocapsule of varying thickness. The tumor extends through normal glandular parenchyma in the form of finger-like pseudopodia, but this is not a sign of malignant transformation.
The tumor often displays characteristic chromosomal translocations between chromosomes #3 and #8. This causes the PLAG gene to be juxtaposed to the gene for beta catenin. This activates the catenin pathway and leads to inappropriate cell division.
The diagnosis of salivary gland tumors utilize both tissue sampling and radiographic studies. Tissue sampling procedures include fine needle aspiration (FNA) and core needle biopsy (bigger needle comparing to FNA). Both of these procedures can be done in an outpatient setting. Diagnostic imaging techniques for salivary gland tumors include ultrasound, computer tomography (CT) and magnetic resonance imaging (MRI).
Fine needle aspiration biopsy (FNA), operated in experienced hands, can determine whether the tumor is malignant in nature with sensitivity around 90%. [3] [4] FNA can also distinguish primary salivary tumor from metastatic disease.
Core needle biopsy can also be done in outpatient setting. It is more invasive but is more accurate compared to FNA with diagnostic accuracy greater than 97%. [5] Furthermore, core needle biopsy allows more accurate histological typing of the tumor.
In terms of imaging studies, ultrasound can determine and characterize superficial parotid tumors. Certain types of salivary gland tumors have certain sonographic characteristics on ultrasound. [6] Ultrasound is also frequently used to guide FNA or core needle biopsy.
CT allows direct, bilateral visualization of the salivary gland tumor and provides information about overall dimension and tissue invasion. CT is excellent for demonstrating bony invasion. MRI provides superior soft tissue delineation such as perineural invasion when compared to CT only. [7]
Overall, the mainstay of the treatment for salivary gland tumor is surgical resection. [9] Needle biopsy is highly recommended prior to surgery to confirm the diagnosis. More detailed surgical technique and the support for additional adjuvant radiotherapy depends on whether the tumor is malignant or benign.
Surgical treatment of parotid gland tumors is sometimes difficult, partly because of the anatomical relationship of the facial nerve and the parotid lodge, but also through the increased potential for postoperative relapse. [9] [10] [11] Thus, detection of early stages of a tumor of the parotid gland is extremely important in terms of prognosis after surgery. [12]
There have been several approaches for surgery of parotid pleomorphic adenoma in the course of time. Enucleation of the tumor (i.e. intracapsular dissection), a procedure that was common in the early 20th century, is nowadays obsolete due to very high incidence of recurrence. [9] After the time of enucleations, pleomorphic adenomas of parotid gland were recommended to be routinely treated with superficial or total parotidectomy. [13] These procedures combine complete tumor removal and identification of the main trunk of facial nerve during surgery to avoid any lesions to the nerve. However, extensive surgery may cause significant morbidity, such as Frey´s syndrome (excessive sweat while eating) and salivary fistula. [14] [15] Also, aesthetic outcome may be compromised. Therefore, less invasive procedures have been preferred in selected cases during the recent years, and introduction of perioperative neuromonitoring enabled the evolution of several different surgical techniques some twenty years ago. [9] [16]
Currently, the choice of surgical approach for parotid pleomorphic adenoma is mainly based on the size, location, and mobility of the tumor. The recommended main techniques include extracapsular dissection, partial superficial parotidectomy, and lateral or total parotidectomy. Nevertheless, the experience of surgeon plays a key role in the results of these distinct procedures. [9] An important point of view is that recurrent pleomorphic adenomas may occur after a very long time from primary surgery, on average over 7–10 years but up to 24 years afterwards. [11] [10] Thus, it is of utmost importance to evaluate the ultimate results of these different surgical techniques in the future.
The benign tumors of the submandibular gland is treated by simple excision with preservation of mandibular branch of the facial nerve, the hypoglossal nerve, and the lingual nerve. [17] Other benign tumors of minor salivary glands are treated similarly.
Malignant salivary tumors usually require wide local resection of the primary tumor. However, if complete resection cannot be achieved, adjuvant radiotherapy should be added to improve local control. [18] [19] This surgical treatment has many sequelae such as cranial nerve damage, Frey's syndrome, cosmetic problems, etc.
Usually about 44% of the patients have a complete histologic removal of the tumor and this refers to the most significant survival rate.
Thyroid neoplasm is a neoplasm or tumor of the thyroid. It can be a benign tumor such as thyroid adenoma, or it can be a malignant neoplasm, such as papillary, follicular, medullary or anaplastic thyroid cancer. Most patients are 25 to 65 years of age when first diagnosed; women are more affected than men. The estimated number of new cases of thyroid cancer in the United States in 2023 is 43,720 compared to only 2,120 deaths. Of all thyroid nodules discovered, only about 5 percent are cancerous, and under 3 percent of those result in fatalities.
The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the mandibular ramus, and secretes serous saliva through the parotid duct into the mouth, to facilitate mastication and swallowing and to begin the digestion of starches. There are also two other types of salivary glands; they are submandibular and sublingual glands. Sometimes accessory parotid glands are found close to the main parotid glands.
An adenoma is a benign tumor of epithelial tissue with glandular origin, glandular characteristics, or both. Adenomas can grow from many glandular organs, including the adrenal glands, pituitary gland, thyroid, prostate, and others. Some adenomas grow from epithelial tissue in nonglandular areas but express glandular tissue structure. Although adenomas are benign, they should be treated as pre-cancerous. Over time adenomas may transform to become malignant, at which point they are called adenocarcinomas. Most adenomas do not transform. However, even though benign, they have the potential to cause serious health complications by compressing other structures and by producing large amounts of hormones in an unregulated, non-feedback-dependent manner. Some adenomas are too small to be seen macroscopically but can still cause clinical symptoms.
Adenoid cystic carcinoma is a rare type of cancer that can exist in many different body sites. This tumor most often occurs in the salivary glands, but it can also be found in many anatomic sites, including the breast, lacrimal gland, lung, brain, Bartholin gland, trachea, and the paranasal sinuses.
An oncocytoma is a tumor made up of oncocytes, epithelial cells characterized by an excessive amount of mitochondria, resulting in an abundant acidophilic, granular cytoplasm. The cells and the tumor that they compose are often benign but sometimes may be premalignant or malignant.
Phyllodes tumors, are a rare type of biphasic fibroepithelial mass that form from the periductal stromal and epithelial cells of the breast. They account for less than 1% of all breast neoplasms. They were previously termed cystosarcoma phyllodes, coined by Johannes Müller in 1838, before being renamed to phyllodes tumor by the World Health Organization in 2003. Phullon, which means 'leaf' in Greek, describes the unique papillary projections characteristic of phyllodes tumors on histology. Diagnosis is made via a core-needle biopsy and treatment is typically surgical resection with wide margins (>1 cm), due to their propensity to recur.
Warthin's tumor, also known as papillary cystadenoma lymphomatosum, is a benign cystic tumor of the salivary glands containing abundant lymphocytes and germinal centers. It is named for pathologist Aldred Scott Warthin, who described two cases in 1929.
Canalicular adenoma is a type of growth that occurs in human salivary glands. It is a benign growth which occurs in the epithelial cells, and is typically arranged in columns of cells that form interconnecting cords. Canalicular adenoma is a very rare benign neoplasm; it constitutes about 1% of all salivary gland tumors and about 4% of all benign salivary gland tumors.
Polymorphous low-grade adenocarcinoma (PLGA) is a rare, asymptomatic, slow-growing malignant salivary gland tumor. It is most commonly found in the palate.
Acinic cell carcinoma is a malignant tumor representing 2% of all salivary tumors. 90% of the time found in the parotid gland, 10% intraorally on buccal mucosa or palate. The disease presents as a slow growing mass, associated with pain or tenderness in 50% of the cases. Often appears pseudoencapsulated.
Salivary gland tumours, also known as mucous gland adenomas or neoplasms, are tumours that form in the tissues of salivary glands. The salivary glands are classified as major or minor. The major salivary glands consist of the parotid, submandibular, and sublingual glands. The minor salivary glands consist of 800 to 1000 small mucus-secreting glands located throughout the lining of the oral cavity. Patients with these types of tumours may be asymptomatic.
Epithelial-myoepithelial carcinoma of the lung is a very rare histologic form of malignant epithelial neoplasm ("carcinoma") arising from lung tissue.
Salivary duct carcinoma (SDC) is a rare type of aggressive cancer that arises from the salivary glands. It is predominantly seen in men and, generally, has a poor prognosis. Other high grade carcinomas can mimic SDC. About 40-60% of SDC arise in pleomorphic adenomas. Most, if not all, SDCs express androgen receptor by immunohistochemistry. Therapeutically relevant genetic alterations include ERBB2/Her2 amplification, PIK3CA and/or HRAS mutations.
Myoepithelioma of the head and neck, also myoepithelioma, is a salivary gland tumour of the head and neck that is usually benign. When malignant, which is exceedingly rare, they are known as malignant myoepithelioma or Myoepithelial carcinoma, and they account for 1% of the salivary tumors with poor prognosis.
Epithelial-myoepithelial carcinoma (EMCa) is a rare malignant tumour that typically arises in a salivary gland and consists of both an epithelial and myoepithelial component. They are predominantly found in the parotid gland and represent approximately 1% of salivary gland tumours.
A sialoblastoma is a low-grade salivary gland neoplasm that recapitulates primitive salivary gland anlage. It has previously been referred to as congenital basal cell adenoma, embryoma, or basaloid adenocarcinoma. It is an extremely rare tumor, with less than 100 cases reported worldwide.
Ceruminous adenocarcinoma is a malignant neoplasm derived from ceruminous glands of the external auditory canal. This tumor is rare, with several names used in the past. Synonyms have included cylindroma, ceruminoma, ceruminous adenocarcinoma, not otherwise specified (NOS), ceruminous adenoid cystic carcinoma (ACC), and ceruminous mucoepidermoid carcinoma.
Carcinoma ex pleomorphic adenoma is a type of cancer typically found in the parotid gland. It arises from the benign tumour pleomorphic adenoma.
A parotidectomy is the surgical excision (removal) of the parotid gland, the major and largest of the salivary glands. The procedure is most typically performed due to neoplasms (tumors), which are growths of rapidly and abnormally dividing cells. Neoplasms can be benign (non-cancerous) or malignant (cancerous). The majority of parotid gland tumors are benign, however 20% of parotid tumors are found to be malignant. Parotidectomy is performed mostly by oral and maxillofacial surgeon and ENT surgeon.
Chronic sclerosing sialadenitis is a chronic (long-lasting) inflammatory condition affecting the salivary gland. Relatively rare in occurrence, this condition is benign, but presents as hard, indurated and enlarged masses that are clinically indistinguishable from salivary gland neoplasms or tumors. It is now regarded as a manifestation of IgG4-related disease.