Ikuko Ogawa

Synovial chondromatosis (SC) is a rare benign disease involving multifocal generation of ectopic cartilage in the synovial tissue. Herein, we report two cases of SC in the temporomandibular joint: a 38-year-old woman (patient 1) and 39-year-old woman (patient 2). Both patients had trismus, jaw joint noises, and jaw-opening pain in the temporomandibular joint. Cone-beam computed tomography (CT) and magnetic resonance imaging (MRI) in patient 1 showed multiple calcified loose bodies around the right mandibular condyle. In addition, CT and MRI in patient 2 showed multiple calcified loose bodies around the left mandibular condyle and temporal bone perforation. Following establishing a diagnosis of SC, both patients underwent tumor resection via open surgery. In immunohistochemical examinations of the resected tissues, tumor cells showed intense nuclear staining with labeled anti-Gli1 antibody. Gene sequencing revealed that both patients had a homozygous mutation in the Gli1 gene (rs2228226 G>C). In conclusion, we suggest that the Gli1 gene (rs2228226 G>C) may be involved in the etiology of SC.

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.

Dedifferentiated salivary gland tumor is a rare, recently recognized tumor type. A case of dedifferentiated malignant myoepithelioma in a 59‐year‐old man who presented with a painful mass in the left preauricular region is reported. Histologically, two distinct neoplastic cell populations were observed in the same tumor mass. The first population was composed of solid nests of polygonal eosinophilic or glycogen‐rich clear cells showing neoplastic myoepithelial immunocytological features, such as positivity for cytokeratins, vimentin, S‐100 protein (S‐100), α‐smooth muscle actin (SMA) and glial fibrillary acidic protein (GFAP). A multinodular growth pattern, necrosis and occasional mitotic figures suggested malignancy. This population was diagnosed as low‐grade malignant myoepithelioma. The second population infiltrated diffusely into the parotid gland and facial nerves. It consisted of polygonal or short spindle cells with obvious pleomorphism and atypical mitoses. The tumor cells were positive for vimentin and cytokeratins, and showed an accumulation of p53 and cyclin D1. S‐100 protein, SMA and GFAP were negative. This population was regarded as undifferentiated carcinoma. A final diagnosis of dedifferentiated malignant myoepithelioma was made. This seems to be the first published case of dedifferentiation in malignant myoepithelioma. Because any tumor type can undergo dedifferentiation with accumulation of additional genetic changes, complete sampling should be the standard approach to all salivary gland tumors in order to avoid missing a dedifferentiation component.

We report an interesting case of pleomorphic adenoma (PA) with extensive adenoid cystic carcinoma (ACC)‐like cribriform areas of parotid gland along with a discussion of the differential diagnosis. T...

A rare case is described of a solitary fibrous tumor (SFT) with malignant potential arising in the sublingual gland. A 59‐year‐old man presented with a 4‐month history of a slowly enlarging painless mass in the center of the floor of the mouth. The tumor was a well‐demarcated, firm mass with a multicystic lesion. The tumor exhibited highly cellular areas of spindle cells with patternless architecture alternating with hypocellular areas. The tumor cells were positive for CD34 and bcl‐2 as well as vimentin, and negative for epithelial, myogenic, neurogenic and histiocytic markers. The tumor cells formed multiple satellite nodules around dilated ducts in the multicystic lesion, indicating infiltrative growth. In addition, areas exhibiting higher cellularity with increased mitoses were noticed in the satellite nodules, although cellular atypia was not obvious. These findings led to a final diagnosis of SFT with malignant potential. There has been no recurrence or metastasis for 27 months after the surgery. Solitary fibrous tumor of the salivary gland must be differentiated from various spindle cell neoplasms including myogenic, peripheral nerve sheath, fibroblastic and fibro‐histiocytic spindle cell neoplasms, hemangiopericytoma and myoepithelioma. In addition to characteristic morphological features, an immunohistochemical positivity for CD34 and bcl‐2 may aid in the diagnosis of SFT.