This article is on Pleomorphic Adenomas. It is intended to help inform patients, relatives of patients and health professionals. The information in the grey boxes is more technical and intended more for Health professionals that are reading this article

 

What is a Pleomorphic Adenoma?

These are non-malignant tumors that arise from salivary gland tissue, also known as benign mixed tumors (BMTs), are the most common salivary gland tumors. The salivary glands contain tissues that produce saliva. Saliva is important to the body because it, helps keep the mouth moist, contains enzymes that break down food and it helps prevent infections of the mouth and throat. There are 3 major clusters of salivary glands.

  • Parotid Glands (84%)
  • Submandibular Glands (8%)
  • Sublingual Glands (0.5%)
  • Minor salivary glands: (6.5%) (widely distributed including the nasal cavity, pharynx, larynx, trachea)

 

Pleomorphic Adenoma

 Benign tumor subtypes

  • Pleomorphic adenoma (benign mixed tumor)
  • Papillary cystadenoma lymphomatosum (Warthin’s tumor)
  • Oncocytoma
  • Monomorphic adenoma, including basal cell adenoma,
  • Sebaceous lymphadenoma
  • Papillary ductal adenoma
  • Benign lymphoepithelial lesion

Malignant tumor subtypes

  • Carcinoma ex pleomorphic adenoma
  • Mucoepidermoid carcinoma
  • Hybrid basal cell carcinoma–adenoid cystic carcinoma
  • Adenoid cystic carcinoma
  • Acinic cell carcinoma
  • Adenocarcinoma
  • Polymorphous low-grade adenocarcinoma
  • Oncocytic carcinoma (malignant oncocytoma)
  • Clear cell carcinoma
  • Epithelial-myoepithelial carcinoma of intercalated ducts
  • Squamous cell carcinoma
  • Undifferentiated carcinoma
  • Metastatic carcinoma

 

Who gets Pleomorphic Adenomas?

Pleomorphic adenomas account for 70-80% of benign salivary gland tumors and are especially common in the parotid gland [1.4,1.5]. Patients are typically middle aged and the incidence is slightly higher in females than males 2:1 [1.4, 1.6]

Pleomorphic adenomas are also commonly found in the lacrimal glands where they account for approximately 50% of lacrimal gland tumors [1.8].

What are the causes?

-The oncogenic simian virus (SV40) may play a role in onset or progression
-Prior head and neck irradiation is a risk factor for the development of these tumors [1.6, 1.7].

What are the symptoms?

Patients typically present with a smooth, painless, enlarging mass in the area of the salivary glands.

 

How is it diagnosed?

The main diagnostic test is a Fine Needle Aspirate usually with Ultrasound guidance. And the cells are viewed under a microscope

Pleomorphic adenomas are composed of a mixture of variable histology. They contain both epithelial and myoepithelial (mesenchymal) tissues, with mixed histology.

They appear encapsulated and well-circumscribed however the pseudo-capsule is delicate and incomplete with microscopic extensions reaching beyond it, accounting for the high risk of recurrence when these tumors are enucleated.

 

What are the Treatment/ Management options?

Surgical excision is curative; however, there is a significant rate of recurrence in the tumor bed. Exact rates of recurrence vary widely depending on series and surgical technique 1-50% [1.4] .The recurrence is attributed to the fact that these tumors are poorly encapsulated and thus there is a high possibility of seeding during surgical excision.

 

Can you prevent pleomorphic adenomas?

You cannot absolutely prevent any form of cancer from occurring, but one can optimally reduce the probability of developing these diseases by avoiding the risk factors, which are known from numerous studies to dramatically increase the risk of developing cancers

 

What is the prognosis?

The prognosis is overall very good for pleomorphic adenomas, surgical resection with appropriate margin is considered curative .if the tumour capsule is breeched during the operation (Enucleation); this is associated with 15 – 25% risk of local recurrence. Recurrences are usually within 18 months but can be up to 50 years later. The risk of malignant transformation is ~5% [1.9]

Risk factors for malignant transformation:
– Multiple recurrences,
– Submandibular location,
– Older age,
– Larger size,
– Prominent hyalinization,
– Increased mitotic rate
– Radiation exposure

 

What are the day to day impacts?

The concerns associated with a pleomorphic adenoma are mainly aesthetic, as they have no invasive or erosive characteristics and reside very superficially in salivary glands they are relatively dormant tumours , and an uncomplicated surgical resection usually fully curative.

 

Further reading:

1) The patient Resource.com

 

References:

1.1. Oral and Oropharyngeal Cancer: Statistics
Statistics adapted from the American Cancer Society’s (ACS) publication, Cancer Facts & Figures 2020, and the ACS website (January 2020).
1.2 Sociodemographic differences in the incidence of oropharyngeal and oral cavity squamous cell cancers in New Zealand
Australian and New Zealand journal of Public Health
First published: 31 March 2015
1.3 National institute of Dental and craniofacial Research
Source: Surveillance, Epidemiology, and End Results (SEER) Program, National Cancer Institute
Surveillance Research Program, based on previous submissions of SEER data (1977-2003)
1.4 Thoeny HC. Imaging of salivary gland tumours. Cancer Imaging. 2007;7 : 52-62. doi:10.1102/1470-7330.2007.0008 – Free text at pubmed – Pubmed citation
1.5 Moonis G, Patel P, Koshkareva Y et-al. Imaging characteristics of recurrent pleomorphic adenoma of the parotid gland. AJNR Am J Neuroradiol. 2007;28 (8): 1532-6. doi:10.3174/ajnr.A0598 – Pubmed citation
1.6 Maria R. Bokhari, Joshua Greene. Pleomorphic Adenoma. (2019) Pubmed
https://radiopaedia.org/articles/pleomorphic-adenoma-of-the-salivary-glands
1.7 Gündüz AK, Yeşiltaş YS, Shields CL. Overview of benign and malignant lacrimal gland tumors. (2018) Current opinion in ophthalmology. 29 (5): 458-468. doi:10.1097/ICU.0000000000000515 – Pubmed
1.8 Karcioğlu ZA. Orbital tumors, diagnosis and treatment. Springer Verlag. (2005) ISBN:038721321X. Read it at Google Books – Find it at Amazon
1.9 Arch Pathol Lab Med 2008;132:1445 [http://www.pathologyoutlines.com/topic/salivaryglandspleomorphicadenoma.html. Accessed June 29th, 2020.]

 

Author + Affiliation:
Dr Tonye Onyemelukwe, Department of Otolaryngology, Waikato Hospital.
Reviewed by Dr James Sanders, Otolaryngology, Waikato Hospital.

Date of Publication +/- Review:
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