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Epidemiology and Demographics

Incidence

  • The annual incidence of Pleomorphic adenoma is approximately 2-3.5 cases per 100,000 population.[1]
  • It accounts for 45-75% of all salivary gland neoplasms.
  • Pleomorphic adenoma distribution among the salivary glands is as follows[2]:
    • Parotid gland: 84%
    • Submandibular gland: 8%
    • Minor salivary glands: 6.5%

Age

  • People of all age groups may develop Pleomorphic adenoma.[1]
  • The incidence of Pleomorphic adenoma increases with age; the average age at diagnosis is 43-46 years.

Race

There is no racial predilection to Pleomorphic adenoma.

Gender

  • Females are predominantly affected by Pleomorphic adenoma than males. The female to male ratio is approximately (2:1)

Causes

  • The exact causes of Pleomorphic adenoma are unknown but the tumor has been found to increase 15-20 years after radiation exposure.
  • Simian virus(SV40) may play a role in the development of Pleomorphic adenoma.[3]

Risk factors

Prior head and neck irradiation is a risk factor for the development of Pleomorphic adenoma.[4]

Classification

  • pleomorphic adenoma can be classified on the basis of the epithelial and stromal changes into the following subgroups.[5]
    • Subgroup 1 (30,5%) is the classical pleomorphic adenoma with a stroma content of 30-50%
    • subgroup 2 (55%) has a stroma content of 80%
    • subgroup 3 (9%) has a poor stroma content of 20-30% or less and an epithelial differentiation similar to subgroup 1
    • subgroup 4 has also a poor stroma content (6%) with a relatively monomorphic epithelial structure.


References

  1. 1.0 1.1 Pinkston JA, Cole P (June 1999). "Incidence rates of salivary gland tumors: results from a population-based study". Otolaryngol Head Neck Surg. 120 (6): 834–40. doi:10.1016/S0194-5998(99)70323-2.
  2. Zhan KY, Khaja SF, Flack AB, Day TA (April 2016). "Benign Parotid Tumors". Otolaryngol. Clin. North Am. 49 (2): 327–42. doi:10.1016/j.otc.2015.10.005. PMID 27040584.
  3. Martinelli M, Martini F, Rinaldi E, Caramanico L, Magri E, Grandi E, Carinci F, Pastore A, Tognon M (October 2002). "Simian virus 40 sequences and expression of the viral large T antigen oncoprotein in human pleomorphic adenomas of parotid glands". Am. J. Pathol. 161 (4): 1127–33. doi:10.1016/S0002-9440(10)64389-1. PMC 1867276. PMID 12368186.
  4. Gündüz AK, Yeşiltaş YS, Shields CL (September 2018). "Overview of benign and malignant lacrimal gland tumors". Curr Opin Ophthalmol. 29 (5): 458–468. doi:10.1097/ICU.0000000000000515. PMID 30028745.
  5. Seifert G, Langrock I, Donath K (December 1976). "[A pathological classification of pleomorphic adenoma of the salivary glands (author's transl)]". HNO (in German). 24 (12): 415–26. PMID 1002574.