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**subgroup 3 (9%) has a poor stroma content of 20-30% or less and an epithelial differentiation similar to subgroup 1 | **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. | **subgroup 4 has also a poor stroma content (6%) with a relatively monomorphic epithelial structure. | ||
==Natural history, Complications and Prognosis== | |||
===Natural history=== | |||
===References=== | ===References=== | ||
{{reflist|2}} | {{reflist|2}} | ||
Revision as of 16:43, 9 January 2019
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]
- Environmental factors
- Occupations like working in rubber industry, nickel industry etc.[5][6]
Classification
- Pleomorphic adenoma can be classified on the basis of the histological appearance i.e, epithelial and stromal changes into the following subgroups.[7]
- 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.
Natural history, Complications and Prognosis
Natural history
References
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ 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.
- ↑ Swanson GM, Burns PB (August 1997). "Cancers of the salivary gland: workplace risks among women and men". Ann Epidemiol. 7 (6): 369–74. PMID 9279445.
- ↑ Horn-Ross PL, Ljung BM, Morrow M (July 1997). "Environmental factors and the risk of salivary gland cancer". Epidemiology. 8 (4): 414–9. PMID 9209856.
- ↑ 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.