Mucoepidermoid carcinoma of the major salivary glands: clinical and histopathologic analysis of 234 cases with evaluation of grading criteria.

BACKGROUND: The authors had previously conducted an investigation of minor salivary gland mucoepidermoid carcinoma, in which they demonstrated that certain clinical and histopathologic features were useful in predicting biologic outcome. The current study investigated the usefulness of these features in determining the prognoses of patients with mucoepidermoid carcinomas of the major salivary glands.

METHODS: Clinical data and 15 histopathologic features were compared in 4 patient groups based on outcome after initial treatment. The outcome groups were 1) survival without disease, 2) survival with tumor recurrence only, 3) survival with metastasis, and 4) death related to tumor. A numeric score was assigned to each unfavorable histopathologic feature. Low grade tumors had scores of 0-4. Intermediate grade tumors scored 5 or 6. High grade tumors had scores higher than 6.

RESULTS: Most patients (75%) were tumor free after the initial treatment. Twenty-one patients (9%) had local recurrence only, 12 (5%) demonstrated metastasis and survived, and 25 patients (11%) died of their disease.

CONCLUSIONS: Clinical features associated with metastasis or death were more advanced age, tumor size, and preoperative symptoms. Histopathologic features that correlated with poor outcome were cystic component less than 20%, 4 or more mitotic figures per 10 high-power fields, neural involvement, necrosis, and anaplasia. All five of these histopathologic features demonstrated statistical prognostic significance when parotid gland tumors from Groups 1 and 4 were compared (P < 0.001). The point-based grading system demonstrated a statistically significant correlation with outcome for parotid tumors but not for submandibular tumors. The authors' findings indicate that patients with tumors of equal histopathologic grade have a better prognosis when their tumors are in the parotid gland than when their tumors are in the submandibular gland. Six of eight submandibular tumors that metastasized or resulted in death were low grade lesions, and none were high grade.