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Pulmonary Pathology Online

Pathology of Pulmonary Epithelial-Myoepithelial Carcinoma

Dr Sampurna Roy MD   

Primary lung tumors mimicking the salivary gland-type neoplasms are extremely rare. These types of tumors originate from submucosal bronchial glands.

Epithelial-myoepithelial carcinoma was first described in salivary glands in 1972  and has been recently incorporated into the World Health Organization's classification system.

Although the tumor has been described in the salivary glands, sweat glands, and breast, epithelial-myoepithelial carcinoma is extremely rare in the respiratory tract.

Microscopic features:

Microscopically, it was composed of two cellular types-epithelial cells with eosinophilic cytoplasm and clear myoepithelial cells.

Numerous tubules formed by an inner epithelial and outer myoepithelial layer were found.

Focally, the tumor showed solid growth of clear cells.

Prominent hyalinization of the stroma was found. 

According to some reports focal atypia and increased mitotic activity may be present, but no vascular invasion or nodal metastasis was identified.

Immunohistochemical findings:

The inner layer of glandular cells has characteristic features of epithelial cells, with extensively positive staining for cytokeratin and epithelial membrane antigen, whereas the outer layer of myoepithelial cells showed strong positivity for S100 protein and smooth muscle actin.

Differential diagnosis:

The differential diagnosis of Epithelial-Myoepithelial carcinoma (EMC) includes mucoepidermoid carcinoma, acinic cell carcinoma, pulmonary pleomorphic adenoma, adenoid cystic carcinoma, myoepithelioma, myoepithelial carcinoma, clear cell ("sugar") tumour, metastatic EMC, and primary and metastatic clear cell carcinomas.

Epithelial-Myoepithelial carcinoma (EMC) differs from pleomorphic adenomas by its absence of myxoid or chondroid stroma.

Adenoid cystic carcinoma with a tubular pattern and its peripheral myoepithelial cell layer may be confused with Epithelial-Myoepithelial carcinoma (EMC).

Adenoid cystic carcinoma differs from Epithelial-Myoepithelial carcinoma (EMC) in that the former has a characteristic cribriform growth pattern and extensive infiltrative growth.

Additionally, perineural infiltration, a common feature of adenoid cystic carcinoma, is absent in Epithelial-Myoepithelial carcinoma (EMC).

Neither myoepithelioma nor myoepithelial carcinoma consists of 2 cell types.

Clear cell ("sugar") tumour of the lung usually occurs peripherally and has a sinusoidal vascular pattern and large, polygonal clear cells with abundant glycogen.

In contrast to EMC, clear cell tumor of the lung is a monophasic tumour, and the cells are HMB-45 positive but negative for cytokeratin.

Primary and metastatic clear cell carcinomas may provide a diagnostic confusion.

The presence of a biphasic pattern and positivity for S100 protein and actin are the characteristics of primary pulmonary EMC and are useful in differentiating it from metastatic clear cell carcinomas.

A review of published cases shows the majority of tumors behave in an indolent fashion, the rare aggressive tumors being predominantly myoepitheliomatous.

The term epithelial-myoepithelial carcinoma is preferred because of their malignant potential.

A high mitotic rate, tumoral necrosis, and nuclear pleomorphism appear to be adverse prognostic factors.

Although follow-up on reported cases is limited, lobectomy with negative bronchial margin should be curative.

 

Further reading:

Bronchial epithelial-myoepithelial carcinoma.

Bronchial epithelial-myoepithelial carcinoma.

Epithelial-myoepithelial carcinoma of the lung. A case report and review of the literature.

Epithelial-myoepithelial carcinoma of the lung: immunohistochemical and ultrastructural observations and review of the literature.

Epithelial-myoepithelial tumor of the bronchus.

Epithelial-myoepithelial carcinoma of the bronchus.

Epithelial myoepithelial tumour of the tracheal gland.

Primary salivary clear cell tumors--a diagnostic approach: a clinicopathologic and immunohistochemical study of 20 patients with clear cell carcinoma, clear cell myoepithelial carcinoma, and epithelial-myoepithelial carcinoma.

 

 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


 

 

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