Myoepithelial Carcinoma Ex Pleomorphic Adenoma of the Maxillary Sinus: A Case Report and Review of Literature

Recurrent pleomorphic adenoma: unusual cause of isolated sphenoid sinus lesion

Pleomorphic adenoma is the most common benign salivary gland tumour of the head and neck region, most commonly seen in parotid glands. These may arise also from minor salivary glands of the upper aerodigestive tract comprises the upper lip, cheek, floor of the mouth and rarely from mucoserous glands in the nasal cavity and paranasal sinuses. A middle-aged man, who had undergone surgery for a nasal mass 14 years ago, presented with headache and visual complaints from a recurrent mass originating from the sphenoid sinus. Isolated sphenoid sinus space-occupying lesions have always been a diagnostic challenge. The mass was biopsied and diagnosed as pleomorphic adenoma on histopathology, and then excised endoscopically. Early and accurate diagnosis on a biopsy may result in complete excision of the tumour and prevent recurrence. The endoscopic route is preferred for surgical excision and the patient should be followed up clinically and radiologically to detect early recurrence.

Maxillary Sinus Pleomorphic Adenoma: A Systematic Review

Background: Pleomorphic adenoma (PA), also known as a mixed tumor, is a neoplasm of the glandular tissue. The maxillary sinus (MS) is an atypical location of PA; however, as an empty cavity inside the bone, it predisposes tumors to develop unnoticed. The aim of the following systematic review was to identify and characterize the diagnostics and prognosis of maxillary sinus pleomorphic adenoma (MSPA). Methods: The cases of MSPA that underwent treatment and were observed for possible recurrence were qualified for the review. The medical databases were searched using the following engines: ACM, BASE, Google Scholar and PubMed. The risk of bias was assessed using the JBI Critical Appraisal Tool for Case Reports. The extracted data were tabulated and summarized in a descriptive manner. Results: To the best knowledge of the authors, only seven cases of MSPA were described in the last 20 years. Relapse occurred in three of these cases and malignant transformation occurred in two. The longest recorded time without recurrence was 4 years. The size of the detected MSPA in the largest dimension ranged in various cases from 40 to 60 mm, with an average of 48 mm. Discussion: All but one of the seven included reports showed flaws during the risk of bias assessment. Only in two of seven reported cases was there no reason to suspect that the tumor had penetrated the sinus from the oral or nasal cavity. The MS is disadvantageous as a location as tumors occupying the entire volume of the sinus are often diagnosed. Recurrences and malignant transformations seem to be frequent and often remain undetected for a prolonged period. Other information: This research received no external funding. OSF Registries number: 8KVGM.

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.