Primary high-grade mucoepidermoid carcinoma of the lacrimal gland: retrospective clinical-pathologic analysis of 20 cases.

BACKGROUND: Primary high-grade lacrimal gland (LG) mucoepidermoid carcinoma (MEC) is a rare condition that presents diagnostic and treatment challenges. In this study, we aimed to elucidate the diagnosis, treatment, and mutational landscape of high-grade LG MEC. METHODS: We reviewed clinical symptoms, radiological images, treatment, prognosis, histopathology, and mutational landscape of 20 patients with high-grade LG MEC. RESULTS: Primary clinical presentation of high-grade LG MEC was proptosis (85%) with a low incidence of ocular pain (20%). CT scans showed frequent bone destruction (89.5%) and calcification (73.7%). MRI revealed hypointense areas on T2-weighted imaging (WI) in 85% of lesions and non-enhanced areas on contrast-enhanced T1WI in 95% of cases. All 20 patients with primary high-grade LG MEC underwent surgery and were stratified into 5 treatment groups. Multi-group analysis showed only the complete resection plus adjuvant radiotherapy group had significantly better RFS than the complete resection alone group (both P = 0.0016), with no significant OS differences across groups. The rates of recurrence, metastasis, and mortality for patients in T4 stage were 77.8%, 71.4%, and 100%, respectively, while those in stages T1-3 were 25%, 75%, and 62.5%. Log-rank tests demonstrated superior long-term RFS and OS in T1–3 patients (P < 0.05), whereas Gehan-Breslow-Wilcoxon tests yielded non-significant results. Whole-exome sequencing of tumors and adjacent normal tissues from 3 patients showed TP53 as the only consistent driver gene with missense mutations in all samples. Additionally, EGFR, DOCK2, GAN11, AKAP9, and SMC4 were identified as driver genes in 2 patients. CONCLUSIONS: High-grade LG MEC predominantly manifested as painless exophthalmos and the characteristic imaging included calcification, bone destruction, hypointense areas on T2WI, and non-enhanced areas on contrast-enhanced T1WI. Adjuvant radiotherapy after complete resection reduced recurrence and improved RFS but did not significantly elevate the overall survival rate of primary high-grade LG MEC patients. Prognosis is especially poor for T4 stage. Potential somatic variants identified within this small exploratory cohort, including TP53, EGFR, DOCK2, GAN11, AKAP9, and SMC4 may represent the potential therapeutic targets. Nevertheless, their clinical and prognostic relevance requires rigorous validation in larger independent patient cohorts.