Report of a case of acinic cell carcinoma of the upper lip and review of Japanese cases of acinic cell carcinoma of the minor salivary glands.

Acinic cell carcinoma (ACC) is a malignant tumor of the salivary glands. The majority of ACCs occur in the parotid gland, and ACCs of the minor salivary glands (MSGs) are relatively infrequent. We describe here a patient with ACC of the upper lip. The patient was a 31-year-old male who presented with a nodular mass on the left upper lip. The preoperative diagnosis was benign tumor or cyst, and the lesion was surgically excised. The histological diagnosis was ACC. The postoperative course was uneventful. No recurrence or metastasis was detected at 13 months postoperatively. In addition, we retrospectively reviewed 21 reported Japanese patients with ACC of the MSGs. In 7 of the 21 patients, the preoperative diagnosis was benign tumor, and the tumors were resected without preoperative biopsy. Kaplan-Meier analysis showed that disease-free survival was worse in patients who underwent resection with a preoperative diagnosis of benign tumor than in patients who underwent resection with a preoperative diagnosis of malignant tumor. The rate of recurrence was higher for ACCs assumed to be benign lesions on a purely clinical basis, or without an accurate preoperative biopsy. ACCs of the MSGs are easy to be misdiagnosed for benign lesions such as mucous cysts or hemangiomas. Correct preoperative diagnosis and initial therapy may therefore be the most important prognostic factors. Key words:Acinic cell carcinoma, Kaplan-Meier analysis, minor salivary glands, prognosis, upper lip.