A ranula is a mucous cyst that forms on one side of the floor of the mouth as a result of damage to the excretory salivary duct. It is a common condition in young people, however congenital cases are rare. We report a case of congenital ranula that grew rapidly to a large size after a mass was noted on the left side of the floor of the mouth during the neonatal examination.

　 A pea-sized mass was identified on the left side of the floor of the mouth during the neonatal examination. An MRI was performed at the age of 1 year and 2 months due to sleep apnea, snoring and a suckling disorder, and an egg-sized mass was found on the floor of the mouth. An experimental puncture aspiration was performed and the ranula was surgically removed under general anesthesia the next day. Histopathological findings showed a mucous extravasated lesion associated with extensive fibrosis with acute and chronic inflammatory cells, leading to a diagnosis of sublingual ranula.

　The possibility of functional impairment such as breathing and suckling disorders should be fully considered in cases of congenital ranula, and follow-up and the timing of surgery should be carefully considered.

Dentigerous cysts are relatively common lesions in the maxillomandibular region. However, it is difficult to distinguish them from odontogenic tumors when the lesion involves a malformed tooth. In this report, we describe a rare case of an odontogenic cyst involving a supernumerary tooth with a dens in dente deformity in the mandibular region. The patient was a 15-year-old boy. At the time of his initial examination, there was mild bony swelling on the 7 buccal side. Panoramic radiography showed a cyst-like radiolucent image in the right mandible from the 7 to the middle of the mandibular ramus, and opaque images with internal transparency to its anterior and posterior. The pathological diagnosis via biopsy was cyst-like lesion. The cyst-like lesion and hard tissue lesion were removed under general anesthesia. The cyst-like lesion was relatively thick, and the pathological diagnosis was dentigerous cyst. One of the hard tissues was a supernumerary tooth with a dens in dente deformity, grayish-white in color, and bullet-shaped. This is a valuable case, since dentigerous cysts originating from a supernumerary tooth with a dens in dente deformity in the mandibular wisdom tooth region are rare, and few cases have been reported in Japan.

Epithelial-myoepithelial carcinoma (EMC) is a rare salivary gland tumor characterized by doublelayered tubular structures composed of inner ductal epithelial cells and outer myoepithelial cells. Accounting for approximately 1% of all salivary gland tumors, EMC occurs primarily in the major salivary glands, particularly in the parotid gland. We report a rare case of EMC thought to have originated from the anterior lingual gland.

　A 68-year-old man visited our department due to awareness of a painful mass in the anterior tongue for one month. A submucosal elastic-hard mass measuring 30 x 25 x 15 mm was found in the anterior lingual region, and a 25 mm large, elastic firm, mobile lymph node was found in the right submandibular region. Contrastenhanced CT and MR images showed relatively clear lesions in the anterior lingual region, and the large lymph node showed contrast effect. FDG-PET/CT showed an accumulation in the anterior lingual region, but no significant accumulation in other areas. Biopsy results suggested adenoid cystic carcinoma. A partial tongue resection and selective right-sided cervical dissection (levels I-IV) were performed under general anesthesia. The histopathological diagnosis was EMC. The primary lesion was curatively resected, and one metastatic lymph node without extracapsular extension was found in the submandibular region (pT3N1). The postoperative course has been uneventful and there have been no signs of recurrence four and a half years after surgery.

We report a case of true kissing molars in the posterior right maxillary molar region. A 39-year-old man was referred to our hospital in February 2021 regarding discomfort in the right molar region. A panoramic radiograph showed an impacted wisdom tooth superimposed on the 7 root and facing an impacted supernumerary tooth at the maxillary tuberosity. In addition, computerized tomography (CT) images showed an impacted wisdom tooth between the buccal and palatal 76 roots with its crown distally upward, sharing a low-density area with an impacted supernumerary tooth with its crown proximally downward. We performed extraction of the impacted supernumerary tooth and 8 tooth and a cystectomy under general anesthesia, using a 3D-printed surgical guide for a proper approach and to avoid 76 root damage. There were no postoperative complications such as abnormal bleeding or epistaxis and no symptoms of postoperative maxillary sinusitis. The patient later reported that the discomfort was gone, and he experienced an uneventful recovery.

Rhinocerebral mucormycosis generally occurs in immunosuppressive conditions such as uncontrolled diabetes mellitus and steroid therapy, and presents acute and aggressive clinical symptoms. Therapeutic strategies for rhinocerebral mucormycosis consist of control of the original immunosuppressive disease, surgery and medication. The prognosis of this condition depends on early diagnosis and treatment. Rhinocerebral mucormycosis rarely presents initial symptoms in the oral cavity. We experienced a case in which rhinocerebral mucormycosis was detected via maxillary osteonecrosis. We played a central role in providing treatment and saving the patient’s life, and his quality of life (QOL) was maintained. The patient was a 62-year-old man who visited our department with severe pain in the left upper molar region. His medical history included rectal cancer with metastatic lung cancer, type 2 diabetes, and coronary spastic angina. Gingival necrosis and sequestrums were observed in the left upper molar region seven days after his first visit. The diagnosis of mucormycosis was made based on micro-fungal biological and pathological samples. Following discussion with related clinical departments, we performed oral surgery twice and a physician provided medication via an antifungal drug. The patient recovered well following treatment. He has returned to work and has been maintaining his QOL over two years under routine follow-up.