DIAGNOSTIC AND PROGNOSTIC UTILITY OF MASTERMIND-LIKE 2 (MAML2) GENE REARRANGEMENT DETECTED BY FLUORESCENT IN-SITU HYBRIDISATION (FISH) IN MUCOEPIDERMOID CARCINOMA. (February 2015) - Luk, Peter P.
Abstract : Aims: Mucoepidermoid carcinoma (MEC) is the most common salivary gland malignancy. A proportion of MECs have been shown to harbour MAML2 translocation. This study evaluates the diagnostic and prognostic utility of MAML2 in MEC. Methods: Salivary gland malignancies at Royal Prince Alfred Hospital and Sydney Head and Neck Cancer Institute (1989–2014) were reviewed to identify MECs. Histopathological evaluation, immunohistochemical and fluorescent in-situ hybridisation (FISH) studies were performed. An additional nine cases of morphological mimics of MEC were also analysed for MAML2 rearrangement. Clinical follow-up was obtained. Results: 40 cases of MEC were identified. Parotid gland was the most common site (73%). The age range was 15–79 years (mean 47 years). The tumour size ranged from 4–70 mm (mean 22 mm). Thirty-seven cases were suitable for FISH and 31 (84%) cases were positive for MAML2 translocation, including oncocytic and clear cell variants of MEC. The nine morphological mimics of MEC did not show MAML2 rearrangement. MAML2 translocation did not correlate with histological grade, stage, nodal metastases, recurrence or survival, limiting its prognostic utility. Conclusion: FISH for MAML2 rearrangement has high sensitivity and specificity for MEC. Thus it is a useful diagnostic tool, particularly in cases with limited material or variant morphology.