Pleomorphic adenoma

Pleomorphic adenoma
Other names	Benign mixed tumor 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

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

The diagnosis of salivary gland tumors utilize both tissue sampling and radiographic studies. Tissue sampling procedures include

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

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]

Treatment

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.

See also

• Warthin's tumor - monomorphic adenoma
• Carcinoma
• Sialadenitis

References