Pleomorphic adenoma is a benign tumour that usually originates in a major salivary gland, sometimes from minor salivary glands and other structures in the head and neck region such as the lip and cheek.
Pleomorphic adenoma of the external auditory canal is an extremely rare disease. This tumour arising in the ear canal was first described in 1951 by Mark and Rothberg.
It is considered to derive from the ceruminous glands of the external auditory canal.
Welti classified these tumors into four groups: Ceruminous Adenoma, Adenoid Cystic Carcinoma, Ceruminous Adenocarcinoma, and the most rare, pleomorphic adenoma. Based on his classification, Syringocystadenoma Papilliferum has been added as a benign neoplasm arising from the ceruminous gland.
The slow growing lesion usually presents as a soft mass covered with epithelium, filling the external auditory canal.
The microscopic examination of pleomorphic adenoma of the ear canal reveals tubuloalveolar and glandular type structures within a fibroadipose, chondroid, myxoid or hyaline stroma.
There is subepithelial proliferation of glandular structures with nests of myoepithelial components in a chondromyxoid stroma, similar to the histology of pleomorphic adenoma of salivary gland origin. Myoepithelial cells of the ceruminous glands are thought to be the origin of primary pleomorphic adenoma of the ear canal. These cells differentiate and can form a component of the tumour.
Malignant transformation of a pleomorphic adenoma of the ear canal has been reported as aggressive 'chondroid syringoma'. In that case, the tumour recurred with cellular atypia and mitotic activity together with many satellite nodules three years after the first resection.
In treating pleomorphic adenoma of the external auditory canal,complete surgical excision is essential for the prevention of recurrence.
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