Pleomorphic adenoma overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
Pleomorphic adenoma also known as ("Benign mixed tumor of the salivary glands") is a benign neoplastic tumor of the salivary glands. It is the most common type of salivary gland tumor and the most common tumor of the parotid gland. In 1874, pleomorphic adenoma was first described by Minssen in a monograph named Ahlbom's. Later Mark and Dahlenfors in 1986 and Bullerdiek et al. in 1987 found some clonal chromosome abnormalities related to pleomorphic adenoma, with a majority of aberrations involving 8q12. Pleomorphic adenoma can be classified on the basis of the histological appearance into 4 subgroups. Subgroup 1 is the classical pleomorphic adenoma with a stroma content of 30-50%, subgroup 2 has a stroma content of 80%, subgroup 3 has a poor stroma content of 20-30%, subgroup 4 has also a poor stroma content (6%). Pleomorphic adenoma shows chromosomal transpositions mainly involving PLAG1 and HMGA2. Pleomorphic adenoma's are usually firm, mobile, well demarcated and encapsulated on gross apperance. On microscopy it is characterized by both epithelial elements and stromal matrix which can be either hyaline, myxoid or cartilaginous. The incidence of Pleomorphic adenoma is approximately 2-3.5 cases per 100,000 population. Females are predominantly affected by Pleomorphic adenoma than males. The various risk factors for the development of pleomorphic adenoma are prior irradiation to head and neck, working in rubber, asbestos industries. The most common presentation is a painless, slow growing and single palpable mass. Pleomorphic adenoma is usually asymtomatic but some people present with dysphagia, hoarseness, difficulty with chewing. MRI is the imaging modality of choice for pleomorphic adenoma. Total parotidectomy is the mainstay of treatment for pleomorphic adenoma. The complications of parotidectomy include haematoma or haemorrhage, facial nerve palsy, frey's syndrome. The prognosis of pleomorphic adenoma is excellent after complete surgical excision.