Epithelial-myoepithelial carcinoma ex-pleomorphic adenoma of the parotid gland: report of a rare case with immunohistochemical and genetic analyses

A rare case of epithelial-myoepithelial carcinoma ex pleomorphic adenoma of the parotid gland: Radiologic-pathologic correlation

Carcinoma ex pleomorphic adenoma is a carcinoma that arises from a primary or recurrent benign pleomorphic adenoma. The prevalence of epithelial-myoepithelial carcinoma is low, and this histological type accounting for only 1% of all salivary gland tumors. Here, we report a rare case of Epithelial-Myoepithelial Carcinoma ex pleomorphic adenoma of the parotid gland with a radiologic-pathologic correlation.

Epithelial-myoepithelial carcinoma of the maxillofacial and sinonasal region: a systematic review of presenting characteristics, treatment modalities, and associated outcomes

Epithelial-myoepithelial carcinoma (EMC) is a rare salivary gland malignancy. Controversy exists in the literature regarding the effectiveness of treatment modalities employed in the management of EMC. This systematic review was undertaken to understand the presenting characteristics of EMC and identify the most common treatment modalities and their associated outcomes, in order to help guide an evidenced-based approach to the algorithm of care. The MEDLINE (PubMed) and Embase databases were searched (up to February 23, 2022), and the review was performed in accordance with the PRISMA statement. Fifty-seven studies (51 case reports and six case series) describing 91 cases of EMC were included in this review. In the included studies, a slow-growing painless mass was the most common presenting clinical feature. EMC was most frequently treated with surgery alone (65%). Local disease recurrence occurred in 24% of the cases and metastatic disease in 11%. A positive surgical margin was found to be associated with a higher risk of recurrence (P < 0.001), while adjuvant radiotherapy was associated with a decreased risk of local disease recurrence (P = 0.034). Metastatic disease and multimodal therapy were found to be associated with decreased disease-free and overall survival (all P < 0.05). The current literature supports surgery with clear margins as the mainstay of treatment for EMC of the salivary and seromucous glands of the head and neck. In certain situations, radiotherapy may improve disease-free survival.

Glial Fibrillary Acidic Protein Expression Helps Distinguish Pleomorphic Adenoma from Histologic Mimics

Pleomorphic adenoma (PA) is the most common biphasic type of salivary gland tumour to arise in adults. It is a biphasic tumour composed of both luminal (ductal) cells and abluminal (basal and myoepithelial) cells. Other biphasic salivary gland type tumours, both benign and malignant, can mimic PA, especially on small biopsies. Previous studies have shown that glial fibrillary acidic protein (GFAP) is preferentially expressed in PA and can be useful in the distinction from other salivary gland tumours. However, most of these studies were performed on a small subset of tumour types at a time when the classification of salivary gland type tumours was less refined. The purpose of this study was to assess the expression of glial fibrillary acidic protein (GFAP) in a broad group of both benign and malignant salivary gland tumours. The expression of GFAP was assessed in 99 tumours including 54 PAs, 5 basal cell adenomas, 1 myoepitheliomas, 5 adenoid cystic carcinomas, 6 epithelial-myoepithelial carcinomas (EMCA), 6 mucoepidermoid carcinomas, 7 salivary duct carcinomas, 1 adenocarcinomas NOS, 2 myoepithelial carcinomas, 4 basal cell adenocarcinomas, 5 acinic cell carcinomas and 3 polymorphous adenocarcinomas. Of the malignant cases, 8 were classified as carcinomas ex PA. GFAP was also assessed in 19 concurrent biopsy specimens. GFAP was expressed in the resections of 51 PAs examined (94%). Expression was predominantly strong and diffusely seen in myoepithelial cells. Strong and diffuse GFAP expression was also seen in two EMCAs (33%) and one myoepithelial carcinoma (50%). On biopsy specimens, 100% of PAs and basal cell adenomas expressed GFAP. GFAP was also seen in 1 out of 3 carcinomas ex PAs on biopsies. Almost all PAs show strong and diffuse expression of GFAP. In contrast, most malignant neoplasms that can mimic PA on biopsies show only rare, focal expression. Other benign tumours composed of abluminal/myoepithelial cells also show focal expression of GFAP, highlighting the spectrum these tumours share with PA. Overall, the presence of strong and diffuse GFAP expression can favour a benign neoplasm, specifically a PA, on limited biopsy specimens.