An Unusual Presentation of Mucoepidermoid Carcinoma of the Parotid Gland

A 33-year-old woman was referred to our institution with complaint of an enlarging mass in the right cheek and jaw. She reported that the mass had been present since childhood, but did notice it increasing size over the past few months and requested removal. Physical exam revealed a firm, mobile mass fixed to the right parotid tail. Contrast enhanced CT of the neck demonstrated a 2.1 x 2.2 x 1.9cm predominantly cystic mass in the right parotid gland superficial lobe with a thin peripheral rim of enhancement (Figure 1 & 2). No associated lymphadenopathy was identified. As the lesion was reported to have been present since childhood, a first branchial cleft cyst was favored based on imaging characteristics and location. The mass was found to be predominantly superficial to the fascia intraoperatively and extended minimally into the preparotid fascia at the central aspect. H&E stained images showed a relatively unicystic lesion, lined predominantly by cuboidal to columnar cells, some with possible cilia, with squamoid cells and some mucus producing cells (Figures 3). Mucicarmine stain brightly highlighted the mucin producing cells (Figure 4). Additionally, lesional cells demonstrated expression of MAML2 rearrangement by fluorescence in-situ hybridization. The combination of these findings strongly supported the diagnosis of low grade mucoepidermoid carcinoma.