腮腺嗜酸细胞型黏液表皮样癌2例临床病理报告及文献回顾OA

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,immuno-phenotype,and molecular characteristics of two patients with parotid OMEC were retrospectively analyzed,and the rel-evant 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 pro-portion 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 posi-tive 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 paroti-dectomy at an outside institution,pathological consultation at the Stomatological Hospital of Jilin University demon-strated that the tumor consisted almost entirely of oncocytic cells,exhibited infiltrative growth,and lacked typical mu-cous,epidermoid,and intermediate cells.Fluorescence in situ hybridization confirmed positive mastermind-like tran-scriptional activator 2(MAML2)gene rearrangement,establishing the diagnosis of left parotid OMEC.The patient sub-sequently 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 onco-cytic 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 mark-ers(e.g.,P63 positivity),and detection of characteristic MAML2 gene rearrangement.Complete surgical excision re-mains the treatment of choice.Conclusion OMEC dominated by oncocytic cells carries a high risk of clinical misdiag-nosis.Integrating the assessment of infiltrative histopathological features with immunohistochemistry and molecular de-tection of MAML2 rearrangement is crucial for accurate diagnosis,appropriate assessment of tumor behavior,and opti-mal surgical decision making.