A Case of Mucoepidermoid Carcinoma of the Parotid Gland Arising in a Warthin’s Tumor

Abstract

Warthin’s tumor is the second most commonly occurring benign parotid tumor. As compared to malignant transformation of a pleomorphic adenoma, carcinoma arising from a Warthin’s tumor is extremely rare. A 77-year-old man presented with a slow-growing left upper neck mass. Enhanced CT showed that the mass consisted of 4 tumors, including 2 low-density tumors with capsules on the anterior aspect, 1 heterogeneously enhancing tumor with a capsule, also on the posterior aspect, and 1 irregularly shaped tumor at the center of the other 3 tumors. The diagnosis could not be established preoperatively, because fine needle aspiration cytology suggested a benign tumor, and FDG-PET/CT revealed accumulation in the tumor. We performed partial parotidectomy and neck dissection of level I, II and III lymph nodes, including the tumors. Histopathology revealed the diagnosis of intermediate-grade mucoepidermoid carcinoma in the 2 low-density tumors on the anterior aspect, and the heterogeneously enhancing tumor with a capsule on the posterior aspect was found to be a Warthin’s tumor. A transitional zone between the mucoepidermoid carcinoma and the Warthin’s tumor was observed in the irregularly shaped tumor at the center. FDG-PET/CT excluded the presence of malignancy in any other tumor other than the tumor we treated. Therefore, we concluded that the mucoepidermoid carcinoma arose from the Warthin’s tumor (pT3N0M0, Stage III). Without any additional treatment, the patient has shown no recurrence and been alive for a year now. Thus, it appears that we performed the appropriate surgery for the intermediate-grade mucoepidermoid carcinoma. To date, only 21 cases of mucoepidermoid carcinoma arising in a Warthin’s tumor have been reported in the literature. All the cases were treated with surgery and showed a favorable prognosis.