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10 Basic Facts that you should know about Epithelial Myoepithelial Carcinoma of the Salivary Gland

 

Dr Sampurna Roy MD   

 

 

                                                                    

 

 
        

    

The tumor was mainly composed of a population of large, polygonal clear cells of myoepithelial type arranged in sheets, nests and tubules surrounded by abundant homogeneous, eosinophilic, hyalinized stroma with small inconspicuous vessels.

 

Source: Politi M, Robiony M, Avellini C, Orsaria M. Epithelial-myoepithelial carcinoma of the parotid gland: Clinicopathological aspect, diagnosis and surgical consideration. Annals of Maxillofacial Surgery. 2014;4(1):99-102.

 

 

(1) Epithelial-myoepithelial carcinoma is a rare disease that usually occurs in the parotid gland, but can occur in a variety of sites such as the nasal cavity, paranasal sinus, and base of the tongue.

 

(2) It was first reported by Donath et al. in 1972 and officially classified by the World Health Organization in 1991.

 

(3) It has been noted that epithelial-myoepithelial carcinoma occurs more commonly in women and has a higher incidence in the fifth to eighth decades.

 
 

    

In some areas another population of cells was evident, arranged in ductal structures, surrounded by the clear myoepithelial cells; this population consisted in cuboidal eosinophilic small cells, with uniform, round nuclei, surrounding luminal spaces occupied by eosinophilic proteinaceous material.

 

Source: Politi M, Robiony M, Avellini C, Orsaria M. Epithelial-myoepithelial carcinoma of the parotid gland: Clinicopathological aspect, diagnosis and surgical consideration. Annals of Maxillofacial Surgery. 2014;4(1):99-102.

 

(4) Clinically, epithelial-myoepithelial carcinomas usually appears as a bulky, slowly growing mass within the parotid gland.

 

(5) Epithelial-myoepithelial carcinomas are defined, histologically, by tubular or ductal structures lined by both basal myoepithelial cells and luminal epithelial cells similar to normal intercalated salivary gland ducts.

 

(6) In immunohistochemical analysis, myoepithelial cells in the outer layer are positive for calponin, p63 protein, glial fibrillary acidic protein, S-100 protein, and smooth muscle actin. Epithelial cells in the inner layer are positive for cytokeratin-7 and epithelial membrane antigen.

 

 

(7) Epithelial-myoepithelial are, low grade malignant tumours although some tumours demonstrate more rapid growth and high grade behaviour. Histologically, the high grade tumours show evidence of dedifferentiation which is not seen otherwise. 

 

(8) The criteria proposed to identify more aggressive lesions are a solid growth pattern, nuclear atypia, DNA aneuploidy, necrosis, positive surgical margins and high proliferative activity. These cases usually have a more aggressive behavior and a higher frequency of local recurrences and metastases.

 

(9) The differential diagnosis of epithelial-myoepithelials include primarily adenoid cystic carcinoma, canalicular and basal cell adenoma, myoepithelioma and myoepithelial carcinoma.

 

 - Adenoid cystic carcinoma,like epithelial-myoepithelial carcinoma, is a tumour composed of a dual cell population of epithelial and myoepithelial cells and it can have a morphology similar to that of epithelial-myoepithelial carcinoma in terms of its trabecular pattern, where the prominent hyalinized stroma surrounds and squeezes the tumour cells into thin strands. In contrast to epithelial-myoepithelial carcinoma, these cells are smaller and usually have more hyperchromatic, irregular and angulated nuclei. 

 

- The feature that distinguishes myoepithelioma and myoepithelial carcinoma from EMC is the lack of a ductal cell component, thus, even if the morphology results in misdiagnosis, the immunohistochemistry results help to differentiate these entities.

 

- Canalicular and basal cell adenoma are benign neoplasms composed of basaloid, relatively monomorphous cells arranged in canaliculi, trabeculae and cords, with a morphology that may be confused with Epithelial-myoepithelial carcinoma, however, the stroma of the neoplasia is typically very loose and hypocellular' mainly in canalicular adenoma and the neoplasm is composed exclusively of epithelial cells without a myoepithelial component as confirmed by immunohistochemistry.

 

(10) Epithelial-myoepithelial carcinoma is regarded as a low-grade-malignant tumour, adequate resection with negative soft-tissue margins is the minimum recommended and necessary therapy. Postoperative radiotherapy is performed to reduce local recurrence. The effect of chemotherapy is not yet clear. It is known that tumours >4 cm are often associated with local recurrence. Therefore, when a large tumour is present, it is important to monitor the patientís postoperative status in the outpatient clinic.

 

                                                                    

 

Source:

 

Oh H-J, Do N, Kee K-H, Park J-H. Epithelial-myoepithelial carcinoma arising from the subglottis: a case report and review of the literature. Journal of Medical Case Reports. 2016;10:45.

 

Politi M, Robiony M, Avellini C, Orsaria M. Epithelial-myoepithelial carcinoma of the parotid gland: Clinicopathological aspect, diagnosis and surgical consideration. Annals of Maxillofacial Surgery. 2014;4(1):99-102.

 

Peters P, Repanos C, Earnshaw J, et al. Epithelial-myoepithelial carcinoma of the tongue base: a case for the case-report and review of the literature. Head & Neck Oncology. 2010;2:4. doi:10.1186/1758-3284-2-4.

 

 

 

 


 

 

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