Salivary gland tumors are often considered difficult to diagnose pathologically because of their histological variability and complexity. There were only nine histological types in the first edition (1972) of the WHO classification of salivary gland tumors; however, 35 histological types will be adopted in the 5th edition (2022). This is mainly due to epidemiological data, the recognition of new concepts, advances in immunohistochemistry and the discovery of tumor-specific gene mutations.

　Fine-needle aspiration cytology is a useful tool for the preoperative diagnosis of salivary gland lesions. In recent years, various international reporting formats have become widespread in cytopathology. The Milan System for Reporting Salivary Gland Cytopathology was published in 2018 and is now becoming a global standard. In the Milan System, six tiered cytological categories are used for the practical interpretation and standardization of cytological findings, and the characteristic numerically designated“ risk of malignancy (ROM)” is an effective method for ensuring the appropriate clinical management of salivary gland tumors.

Systemic therapy for salivary gland carcinoma (SGC) is indicated for recurrent and/or metastatic (RM) disease. The background, goals of therapy, organ function, symptomatic or a symptomatic, and histopathology should be considered in each case. Adenoid cystic carcinoma with only lung metastasis often progresses slowly and many cases are followed up without therapy, whereas salivary duct carcinoma, adenocarcinoma NOS, or adenoid cystic carcinoma with multiple metastases, including lung, liver, and bone, often require the early introduction of systemic therapy.

　The selection of drugs for RM SGC is often based on drugs approved for squamous cell carcinoma of the head and neck, and relatively favorable results have been reported for combination chemotherapy with platinum and taxane. On the other hand, in recent years, personalized therapies based on biomarkers have been developed. Two U.S. guidelines already recommend drug selection based on biomarkers of androgen receptor (AR) status, NTRK gene fusion, HER2 status, and tumor mutation burden (TMB): Leuprorelin and Bicalutamide for AR-positive cases, Larotrectinib or Entrectinib for NTRK gene fusion-positive cases, Trastuzumab, Trastuzumab + Pertuzumab, Trastuzumab emtansine, Trastuzumab + Docetaxel, and Trastuzumab deruxtecan for HER2-positive cases, and Pembrolizumab for TMB-high cases, respectively. In Japan, Trastuzumab was approved for HER2-positive SGCs in November 2021.

Oral lichenoid lesion (OLL) is a lesion that causes cell-mediated immune tissue reactions, and is very similar to oral lichen planus (OLP). This disease can be distinguished from OLP when the cause is clear. OLL is often caused by dental metals, drugs and diseases such as graft-versus-host disease(GVHD). The clinical and histopathological differences between OLP and OLL are still under debate. In this study, the clinical and histopathological findings of 11 cases of OLL were retrospectively investigated.

　The study included 11 patients who visited the outpatient clinic for oral mucosal diseases(joint outpatient clinic for oral surgery and dermatology) at the Tokyo Dental College Ichikawa General Hospital and were diagnosed with OLL in cooperation with dermatologists between April 2014 and March 2019. The patients included four males and seven females, with an average age of 56.9 years. Lesions were associated with drugs (4 cases), materials (3 cases), GVHD(2 cases), dental material(1 case) and hepatitis C (1 case). OLL lesions were in the buccal mucosa (9 cases), gingiva (8 cases), dorsum of the tongue(8 cases), lip(6 cases) and sublingual surface (6 cases). The clinical classifications were red type (6 cases) and white type(5 cases), with 6 cases including skin symptoms. Lesions were found in 4.7 sites on average.

　Histopathological findings were consistent with OLP in 11 cases, and no findings characteristic of OLL were observed.

　Immunohistochemical staining for p53 and Ki-67 (carcinogenesis markers) was performed; however, no epithelial positive cell overlay was observed in any of the cases.

The usual treatment for ameloblastic carcinoma is surgical resection. The effectiveness of radiotherapy and chemotherapy for the disease has not been determined, and few effective treatments are available for local recurrence and distant metastasis. Recently, molecular targeting using BRAFV600E inhibitors has attracted interest as a treatment for ameloblastoma and ameloblastic carcinoma.

　Vemurafenib and dabrafenib are BRAF inhibitors that strongly and selectively inhibit BRAFV600E mutant kinases and exhibit anti-tumor effects. Although they are adapted for some malignant melanoma and non-small-cell lung cancer, they are expected to be effective as a molecular targeting therapy for ameloblastoma and ameloblastic carcinoma with BRAFV600E mutation.

　We experienced a case of ameloblastic carcinoma that developed in the maxillary molar region and spread into the maxillary sinus. The patient was a 27-year-old male who presented to our hospital with the chief complaint of swelling and pain in the right maxillary molar region. Under the diagnosis of ameloblastic carcinoma, we performed a total maxillectomy, right neck dissection, and reconstruction with a rectus abdominis myocutaneous flap. Following the surgery, we conducted a BRAFV600E immunohistochemistry examination on the resected tumor and found that the solid and cystic tissues were positive for BRAF mutation.

Cystadenoma is a benign tumor derived from glandular tissue characterized by glandularly growing epithelium forming numerous large cysts. Cystadenoma originating from the retromolar region are extremely rare. We report a case of a giant cystadenoma extending from the retromolar region to the parapharyngeal space.

　The patient was a 64-year-old female. She had noticed swelling in her right mandibular molar region for a year, and visited our department because the swelling was growing gradually. At her first visit, the mucosa of the pharynx was markedly swollen from the posterior part of her right mandibular acetabulum to the oropharyngeal isthmus. The surface of the swelling was smooth and there was no pain, neuropathy, trismus, dyspnea or dysphagia observed. Contrast-enhanced MRI revealed a 40×30×23 mm well-defined mass with multiple cyst formations from the posterior part of the right retromolar region to the parapharyngeal space. A tissue biopsy showed no evidence of malignant tumor; however, it was difficult to determine the histology. We suspected a benign salivary gland tumor and performed surgery under general a nesthesia. The tumor was enucleated as a single mass using the mandibular midline transection method. Histopathological examination revealed large and small cysts lined with epithelial cells with acidophilic columnar and cubic structures, and minor salivary gland tissue was found on the surface of the tumor, so we diagnosed cystadenoma. There has been no tumor recurrence five years after the operation, and the patient is doing well.

Congenital atresia of the submandibular gland duct is a rare congenital anomaly in which an imperforate duct orifice, caused by incomplete formation of the duct during the embryonic period, results in the retention of saliva in the submandibular gland duct. Although its clinical appearance is very similar to that of ranula, they are different disorders and should therefore be differentiated appropriately.

　Herein we report a case of congenital atresia of the submandibular gland duct and a review of the literature on the differences between this congenital anomaly and ranula.

　An 8-month-old male infant was referred to our department due to a ranula-like swelling in the right oral floor, which had been present since birth. We performed magnetic resonance imaging(MRI) and diagnosed the patient with congenital atresia of the submandibular gland duct. We performed marsupialization according to the method for ranula under general anesthesia when the patient was one year and eight months old. The resected specimen was also histologically diagnosed as congenital atresia of the submandibular gland duct. Normal salivary flow from the formed duct orifice was observed and there was no recurrence one year since the operation.

Microsecretory adenocarcinoma is a recently described low-grade salivary adenocarcinoma proposed by Bishop et al. in 2019. This tumor is characterized by unique histologic and immunophenotypic features and detection of the MEF2C-SS18 fusion gene. Herein we report a case of microsecretory adenocarcinoma of the hard palate. A 39-year-old man was referred to our department because of a painless mass that he had been aware of in his hard palate for over 10 years. A well-circumscribed elastic-hard mass 13 × 10 mm in diameter was observed in the posterior part of the left hard palate. An excisional biopsy was performed under local anesthesia. Microsecretory adenocarcinoma was strongly suspected histopathologically and immunohistochemically, therefore molecular analysis via reverse transcriptase polymerase chain reaction was performed. As a result, the MEF2C-SS18 fusion gene was detected and the diagnosis of microsecretory adenocarcinoma was confirmed. There was no evidence of recurrence or metastasis at 15 months after the resection.