Salivary gland neoplasms are uncommon, and their epidemiology in Japan has not been well described. We conducted a retrospective review of salivary gland tumors registered in the Hiroshima Tumor Tissue Registry over a period of 39 years. The subjects were 5015 cases ranging in age from 6 to 97 (mean, 54.3) years old. The incidence of both benign tumors and malignant tumors increased with age until 60–69 years and then declined. Among the 5015 salivary gland neoplasms, 3998 (80%) were benign and 1017 (20%) were malignant. Pleomorphic adenoma (PA) was the most frequent benign tumor (68%), followed by Warthin tumor (26%). Adenoid cystic carcinoma (ACC) (27%) and mucoepidermoid carcinoma (MEC) (26%) were the two most frequent malignant tumors. Characteristically, there was a very low incidence of polymorphous adenocarcinoma in Japan. The average annual age-adjusted incidence rate per 100,000 population was 3.3 for benign tumors and 0.8 for malignant tumors. This is the large-scale multi-institutional analysis to describe the characteristics of salivary gland neoplasms, based on the pathological tissue registry data. We hope that the present data can contribute to early diagnosis and effective treatment of salivary gland tumors and to cancer prevention.

Ossifying fibromyxoid tumor (OFMT) is a rare mesenchymal neoplasm that arises in subcutaneous tissue, with that in the oral cavity extremely rare. We present a case of malignant OFMT in the tongue. A 26-year-old male noticed a painless mass in the tongue, which was extracted at a general hospital. Four years later, the tumor recurred and was resected at our department. Histologically, the recurrent tumor was composed of the closely packed cells positive for vimentin and S-100 proliferating in a nodular fashion. It showed high cellularity and mitotic activity. In the primary tumor, some tumor cells were arranged in a diffuse or cord-like manner within an abundant fibromyxoid matrix, along with a small amount of metaplastic ossification, corresponding with the histopathological characteristic of OFMT. Accordingly, a diagnosis of malignant OFMT arising in typical OFMT was established. This is the first reported case of malignant OFMT in the tongue. Long-term follow-up is needed for confirmation of prognosis and biological behavior.

In this article, we present our experience with a case of myxolipoma of the tongue. Lipoma is a mesenchymal benign tumor occurring with relatively high frequency. However, myxolipoma, one of the histological variant of lipoma characterized by mature adipose tissue and abundant mucoid substances, in the oral cavity is quite rare. The patient was a 52-year-old man who noticed a painless mass on the left border of tongue about 2 years ago. The lesion was noted at a complete medical checkup, and the patient was admitted to our institution for detailed examination. The mass was a palpable, soft and elastic nodule, 15 mm in diameter, covered with normal mucosa in the left inferior aspect of the tongue. The border of the tumor was well-defined, and computed tomography (CT) revealed a fat density within the mass. On the basis of these finding, the tumor was clinically diagnosed as lipoma and was excised under general anesthesia. Histopathologically, the tumor was a well-defined lobulated mass surrounded by a thin fibrous capsule within the muscle of the tongue. The tumor was diagnosed as myxolipoma because it was consisted of solid proliferation of mature adipocytes replaced by abundant mucoid substances. The post operative course was uneventful, and there was no evidence of recurrence 4 years after surgery.