Mucoepidermoid Carcinoma of the Lingual Tonsil.

Intraoral malignant neoplasms of salivary glands are a relative rarity, with less than 3 per cent of tumors of the head and neck arising in them. A review of current literature suggests that mucoepidermoid carcinoma (MEC) is the most common malignant tumor observed in both major and minor salivary glands.13 Composed of differing numbers of epidermoid, intermediate, and mucusproducing cells, they make up about one-third of all salivary gland tumors with approximately 89.6 per cent of them arising in the parotid gland.2 The neoplasms have a slight tendency to occur in women and have the greatest incidence from the third to sixth decade of life.4 MEC is a malignant process, so histological grading is prognostically useful in predicting outcome. Low-grade tumors more often contain cystic spaces and mucinproducing cells predominate, whereas intermediate grade tumors are less cystic and contain more irregular sheets of squamous cells and prominent intermediate cells. High-grade tumors are solid with epidermoid predominance making it appear like squamous carcinoma.4 Although MECs arise in areas like the palate, the buccal mucosa, or the floor of the mouth when in the oral cavity, rarely they have been reported to occur as lacrimal, nasal, laryngeal, breast, or pulmonary tumors.2, 4 We present a rare case of MEC arising from the lingual tonsil. A 31-year-old African American male presented to the clinic with complaints of dysphagia, pain, and swelling in the back of his throat. A CT scan of the neck showed a 2.2-cm mass within the right pharyngeal mucosal space, at the level of the tongue base. The lesion extended into the right vallecula and piriform sinus. Appearing well marginated, it demonstrated homogenous arterial phase contrast enhancement on CT scan. A biopsy of the right lateral pharyngeal wall showed mild sub mucosal edema and congestion with no atypia and negative for malignancy. A subsequent excisional biopsy of the right vallecula showed submucosal lymphoid aggregate and prominence of the submucosal lymphoid components, with surface reactive squamous change and associated foreign material but was again negative for neoplasia. The patient came back to the clinic for follow-up with continuing signs of throat pain, dysphagia, feeling of something in the back of his throat, and poor appetite and was subsequently scheduled for a tonsillectomy. After tonsillectomy of the right lingual tonsil, microscopic examination of the mass showed lymphoid hyperplasia of the right lingual tonsil (Fig. 1). An ensuing CT scan of the neck showed no significant change in the right pharyngeal space mass measuring 1.6 · 1.6 cm extending from the region of the lingual tonsil into the vallecula (Fig. 2). The stable nature of the mass suggested a benign diagnosis. However, another biopsy of the right lingual tonsil showed some benign mucosal and submucosal tissue but some distorted smaller fragments of low-grade invasiveMEC. The tumor showed no neural invasion or necrosis and lacked intracystic components and mitoses of 4/10 High Power Field (HPF). After the biopsy, the patient’s sore throat and hoarseness of voice did not abate and radiology and oncology consults were arranged. The patient was provided adequate pain control and scheduled for follow-up. MEC is the most common malignant neoplasm of salivary glands, arising from reserve ductal cells. However, there have been rare reports of these tumors occurring in breast, thymus, mandible, and pulmonary tissue. To our knowledge, only two other cases of MEC occurring in the tonsils have been reported in literature,2 making our case a rarity. MEC is composed of mucin-producing and epidermoid cells, but there is no distinctive cytology for MECs. When mucoid cells predominate with cystic architecture, the MEC is regarded as low grade, whereas epidermoid predominance with a solid structure is characteristic of high-grade tumors. Low-grade tumors often present with low mitotic figures (<3/10 HPF) with well-circumscribed margins and sizes Presented as a poster at the Southeastern Surgical Congress, February 20 23, 2016. Atlanta, GA. Address correspondence and reprint requests to Roger Su, M.D., Atlanta Cancer Research and Education Foundation, 1136 Cleveland Avenue, Suite 611, East Point, GA 30344. E-mail: office@acraef.org.