We report a case of an odontogenic cyst which developed from a malformed tooth in a six-year-old boy. Preoperative radiography and computed tomography revealed that the cystic lesion was 30 x 25 mm in diameter, with a mixed radiolucent and radiopaque lesion. Upon the provisional diagnosis of odontogenic cyst, the lesion was surgically removed under general anesthesia. Macroscopic analysis showed a cystic lesion with tooth-like hard tissue. Histopathological inspection revealed an inverted malformed tooth with a cyst covered in enamel epithelium. The pathological diagnosis was an odontogenic cyst suspected of being dentigerous. Because of atypical findings in both clinical and X-ray imaging, it was difficult to make an accurate diagnosis before operation. About 18 months have passed since the operation, and no complication has been observed. The patient made favorable progress after the surgery. The pathogenesis of the malformed tooth and its role in cyst formation is still unclear, because only three similar cases have been reported to date. Therefore, we inferred the origins of the cyst based on the etiology of odontogenic cysts in the past. A greater accumulation of cases and analyses will be required to form a general opinion. Moreover, additional cooperation of clinician and pathologist teams will be necessary to ensure accurate diagnosis.

Osteochondroma is a benign bone tumor covered by a cartilage cap, arising at the external surface of the bone. In the oral and maxillofacial regions, this lesion is known to develop in the mandibular condyle; however, involvement of the temporal bone is rare. We present a case of osteochondroma arising at the articular tubercle of the temporal bone. A 32-year-old man visited our department for evaluation of a mass in the right temporal bone. Radiographic examination revealed a pedunculated exophytic mass continuous with the articular tubercle of the right temporal bone, and the patient was clinically diagnosed with a temporal bone tumor. We performed surgical resection through a preauricular incision under general anesthesia. A histopathological evaluation revealed formation of bone covered by a cartilage cap, which confirmed the diagnosis of osteochondroma. The residual lesion showed no growth two years postoperatively.

Merkel cell carcinoma (MCC) is a rare and highly aggressive neuroendocrine malignancy of the skin. We report a case of MCC of the lower lip. An 85-year-old woman was referred to our hospital because of a tumor in her lower lip. An extraoral examination revealed a palpable soft tumor measuring 17 × 11mm. A malignant tumor was suspected, and a FDG-PET/CT was performed. Accumulation was observed in the lower lip, the first spinous process, the right side of the second vertebral body, the left seventh rib, and the right pubis. The lip was resected first, because it was considered to be a bone metastasis of non-Hodgkin's lymphoma, the treatment of which had been discontinued in the past. A pubic biopsy was performed after surgery and MCC with multiple bone metastases was diagnosed. The painful pubis and ischium were irradiated (30Gy/10fr), and Avelumab and Denosumab administered. However, brain metastasis and irAE enteritis were observed, and the patient died of this disease one year and eight months after the initial diagnosis.

Congenital midline upper lip fistula is a very rare congenital anomaly that can be accompanied by other congenital abnormalities such as cleft lip and palate, and may appear as a symptom of a syndrome such as Pirre-Robin’s syndrome. It has been reported that this disease can be transmitted and presents signs of infection such as swelling of the upper lip, abscess formation, and pus discharge from the fistula. However, a case of infection in infancy has never been reported before.

　Here, we report a case of a six-month-old baby with an infected congenital midline upper lip fistula. The patient visited our hospital with swelling of the upper lip and suckling disorder. With the midline upper lip fistula infected, signs of infection such as swelling of the upper lip, pus discharge from the fistula, and dome-shaped swelling of the oral vestibule of the maxillary anterior tooth were observed. Due to these acute symptoms, the patient had a suckling disorder. After anti-inflammatory treatment, we resected the lip fistula under general anesthesia.

　Congenital midline upper lip fistula is likely to cause infection in infancy, leading to a suckling disorder. Early examination and treatment for a congenital midline upper lip fistula is suggested.

This report describes a rare case of a fishbone that penetrated the tongue and moved toward the hyoid bone. An 84-year-old woman was referred to the department with the chief complaint of pain and swelling in her tongue. After anti-inflammatory therapy, a fishbone-like foreign body was detected in the tongue through computed tomographic and ultrasonographic examinations. Since a CT scan performed the day before the operation had revealed that the foreign body had moved from the dorsum of the tongue to near the hyoid bone, it was removed by means of a skin incision, using intraoperative ultrasonography under general anesthesia. The removed foreign body was a needle-shaped 25 mm fishbone. There was no postoperative infection or other complication. In conclusion, it is important to obtain a detailed medical history and to use imaging for detecting foreign bodies in soft tissue and determining their position. Furthermore, it is vital to reconfirm the position just before the operation. Intraoperative ultrasonography is useful for improving the accuracy of the operation because it enables detection of the foreign body in real time.