Objective: To investigate the clinicopathological characteristics and diagnostic-therapeutic strategies of oncocytic mucoepidermoid carcinoma (OMEC) of the parotid gland, and to enhance awareness of this rare variant among clinicians and pathologists. Methods: The clinical data, imaging findings, histopathological features, immunophenotype, and molecular characteristics of two patients with parotid OMEC were retrospectively analyzed, and the relevant literature was reviewed. Results: Case 1 was a 50-year-old man who presented with a painless mass behind the right earlobe for more than 2 years. The patient underwent extended parotidectomy with preservation of the facial nerve. Histopathological examination revealed that the tumor was predominantly composed of oncocytic cells with a small proportion of mucous cells. Immunohistochemically, the tumor cells were partially positive for cytokeratin 5/6, cytokeratin 7, and P63. Special staining with alcian blue, periodic acid-Schiff, and phosphotungstic acid hematoxylin yielded positive results. The diagnosis of right parotid OMEC was established. No recurrence or metastasis was observed during a 1 year follow-up. Case 2 was a 61-year-old man with a 3-month history of a mass beneath the left ear. After partial parotidectomy at an outside institution, pathological consultation at the Stomatological Hospital of Jilin University demonstrated that the tumor consisted almost entirely of oncocytic cells, exhibited infiltrative growth, and lacked typical mucous, epidermoid, and intermediate cells. Fluorescence in situ hybridization confirmed positive mastermind-like transcriptional activator 2 (MAML2) gene rearrangement, establishing the diagnosis of left parotid OMEC. The patient subsequently underwent total parotidectomy with preservation of the facial nerve, and no recurrence was detected during a short-term 3 months follow-up. A review of the literature indicated that OMEC most commonly arises in the parotid gland and is generally a low-grade malignancy with favorable prognosis. When tumors are composed exclusively of oncocytic cells, exhibit minimal cytological atypia, and lack the classical cellular components of mucoepidermoid carcinoma, they are highly prone to misdiagnosis as oncocytoma, nodular oncocytic hyperplasia, or other benign oncocytic lesions. Accurate differential diagnosis relies on recognition of infiltrative growth patterns, supportive immunophenotypic markers (e.g., P63 positivity), and detection of characteristic MAML2 gene rearrangement. Complete surgical excision remains the treatment of choice. Conclusion OMEC dominated by oncocytic cells carries a high risk of clinical misdiagnosis. Integrating the assessment Conclusion OMEC dominated by oncocytic cells carries a high risk of clinical misdiagnosis. Integrating the assessment of infiltrative histopathological features with immunohistochemistry and molecular detection of MAML2 rearrangement is crucial for accurate diagnosis, appropriate assessment of tumor behavior, and optimal surgical decision making.

The basement membrane is a specialized extracellular matrix between the epithelium and the mesenchyme.In stratified epithelium,only the basal cells in contact with the basement membrane exhibit the apical-basal polarity,whereas the epithelial cells do being not in contact with the basement membrane do not exhibit the apical-basal polarity.The basement membrane plays an important role in epithelial cell polarization.It is an important extracellular matrix(ECM)structure in the multicellular organisms,is situated between the epithelium and the mesenchyme,and is produced jointly by the epithelial cells and mesenchymal cells.Its components mainly include Laminin,type Ⅳ collagen(Col-Ⅳ),nidogen(NDG),and heparan sulfate proteoglycans(HSPG),and each component plays the different role in influencing the epithelial cell polarity.The network scaffold formed by Col-Ⅳ and Laminin is the main structure of the basement membrane,and the integrity of the structure affects the epithelial cell polarization.This review summarizes the composition and structure of the basement membrane,focuses on its role in epithelial cell polarization and its mechanism,and compiles the current status of biomimetic basement membrane materials that promotes the epithelial cell polarization,and provides the theoretical foundation for further exploration of the establishment and maintenance of epithelial cell polarity.