Clear Cell Myoepithelioma of Palate with Emphasis on Clinical and Histological Differential Diagnosis

Abstract

Myoepitheliomas account for less than 1% of all salivary gland tumors and mostly occur in the parotid gland and palate. A 58-year old male patient reported to the Outpatient Department of PMS College of Dental Science and Research (Kerala, India) with a slow growing painless swelling on the palate for 4 years. Pleomorphic adenoma, basal cell adenoma, myoepithelioma, cyst adenoma, lipoma, neurofibroma, neurilemmoma and leiomyoma were considered. Histopathology revealed a thinly encapsulated tumor composed mainly of sheets of clear cells mixed with cells having eosinophilic cytoplasm. Histopathological differential diagnosis included pleomorphic adenoma, oncocytoma, oncocytic hyperplasia, sebaceous adenoma, malignant salivary gland neoplasms and metastatic lesions from kidney and thyroid. Myoepitheliomas mostly occur in the parotid gland and palatal region and various histological types of myoepithelioma are described. Myoepitheliomas of the palate are rare with clear cell variant even rarer.

Benign myoepithelioma of the hard palate: a clinical and histological diagnostic challenge. Case report and literature review

“…Previous descriptions suggest that myoepitheliomas can either develop with a full capsule (for the parotid myoepithelioma), or with an irregular capsule [11] (with few interruption zones) or without a capsule (mostly described for palatal myoepithelioma) [12]. The tumor observed in this case was fully encapsulated in a fibrous capsule, in accordance with other description in the same area [4,13] (Fig. 3).…”

“…Although myoepithelioma might occur in any tissue with a secretory function (major and minor salivary glands, sweat glands, lacrimal glands, prostate, breast, nasopharynx, lungs, retroperitoneal region, skin and soft tissue) [4] they preferentially develop in the parotid gland (40%) and in minor salivary glands (21%), especially in the hard and soft palate (40% of reported cases) [3]. Those found in minor glands occur in slightly younger individuals, in compare with other sites [2].…”

Potential Trapping Lesion of the Parotid Gland (Multi-Nodular Oncocytic Hyperplasia): Case Report

“…[1][2][3][4][5][6][7][8][9] The most frequent oncocytic tumor of salivary glands is Warthin's tumor "papillary cystadenoma lymphomatosum" and oncocytic cells can also appear in pleomorphic adenoma. 2,3,7,8 MNOH in the salivary glands is an extremely rare condition representing a multifocal oncocytic proliferation of the duct system. MNOH makes up 0.1% of the parotid gland diseases.…”

“…11 The most frequent oncocytic tumor of salivary glands is Warthin's tumor and oncocytic cells may also be seen in pleomorphic adenoma. 2,3,7,8 Oncocytes may also encountered in some pathological conditions of the salivary glands like diffuse oncocytosis, MNOH, oncocytic metaplasia, oncocytoma and oncocytic carcinoma. Lesions composed entirely of oncocytes fall into three categories-oncocytoma, diffuse oncocytosis and multifocal nodular oncocytic hyperplasia.…”

“…Lesions composed entirely of oncocytes fall into three categories-oncocytoma, diffuse oncocytosis and multifocal nodular oncocytic hyperplasia. [5][6][7][8][9] MNOH is a rare condition that is characterized by the presence of multiple nodules of oncocytic cells and makes up 0.1% of the parotid gland diseases. 7,10 It is mainly diagnosed in women and in the sixth decade and the clinical features may include swelling and tenderness of the parotideal region and duration of the symptoms may be from several months to 25 years duration.…”