Title: Rare Case of Polymorphous Adenocarcinoma at the Base of the Tongue
Author(s): Avi Shaw, DO; Eugene Potesta, MD
Email: Ashaw@mercy.com
Introduction: Polymorphous low-grade adenocarcinoma is a malignant neoplasm that was termed in 1984 by Evans and Batsakis due to the variable structural presentation as well as the low-grade nature. However, more recently, the WHO Classification of Head and Neck Tumors have noted the omission of “low-grade” due to some tumors demonstrating aggressive features. The majority of Polymorphous adenocarcinomas (PAC) have been identified to involve minor salivary glands of the palate, lip, buccal mucosa, alveolar ridge, and mucosal sites, though the palate being predominantly affected. In this report we describe a case of polymorphous adenocarcinoma, a rare presentation of minor salivary gland tumor at the right base of tongue in an elderly female. This article will highlight the importance of proper identification of base of tongue malignancies, review the few, but documented cases of PAC, and discuss the specific treatment options.
Case Report(s): An 85-year-old female with a past medical history of coronary artery disease and diverticulitis presented to the emergency room with an unwitnessed fall. As the patient was being evaluated, there was an incidental finding on CT which at that time showed a 2.8cm right tonsillar/base of tongue mass. She subsequently underwent a direct microlaryngosocpy with biopsy which resulted in polymorphous adenocarcinoma emanating from the right base of tongue. Normally definitive surgical resection is ideal, although in this situation, given the location of the tumor, surgical resection would be extensive and place the carotid artery at great risk. She was seen by radiation oncology and underwent radiation therapy where she received 40 and 50 Gray in a simultaneous integrated boost in 20 fractions over 28 elapsed days to the right hemi-neck and base of the tongue respectively. After radiation treatment was completed, the patient was reassessed and is noted to be doing well with improvements in her taste, however, there was not complete tumor resolution at the time of this report.
Discussion: Polymorphous Adenocarcinoma (PAC), first described back in 1984 as a site of typical blind but architecturally diverse malignant neoplasm of salivary gland origin. It has previously been referred to as terminal duct carcinoma by Batsakis et al. in view of its likely origin in the ductal system of the salivary glands. PAC has been found in a 2:1 female preponderance and almost exclusively in the minor salivary glands with majority of cases identified to predominantly affect the soft and hard palate. Based on literature review there are only a handful of documented cases of PLGA found at the base of the tongue, which is an unusual tumor site for PLGA to occur. PAC is often wrongly diagnosed as ACC. Adenoid cystic carcinoma is an uncommon malignant neoplasm that has been noted to primarily arise in minor salivary glands with the most frequent origin being the palate. Histological features of PAC and ACC contain related structures which include cribriform, tubular, and solid patterns. Similar histopathological characteristics thus presents difficulty when attempting to differentiating between PAC and ACC in minor salivary glands. Therefore, it is imperative to distinguish the two for appropriate therapeutic treatment and prognosis, as adenoid cystic carcinoma is associated with much worse prognosis.
