MAML2 (11q21), Mucoepidermoid Carcinoma (MEC)
Supporting a diagnosis of mucoepidermoid carcinoma
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland neoplasm, representing over 30% of all malignant salivary gland tumors. The diagnosis of MEC can be quite challenging due to the degree of histologic overlap with other glandular, clear cell, or oncocytic salivary gland tumors. MAML2 fusions are detectable in 80% to 85% of MEC, but not in morphologic mimics such as oncocytic cystadenoma, Warthin tumor, oncocytoma, oncocytic carcinoma, acinic cell carcinoma, and metastatic renal cell carcinoma.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-9% rearranged cells
A positive test is consistent with a diagnosis of mucoepidermoid carcinoma (MEC). A negative test does not rule out the diagnosis of MEC. Carcinomas such as salivary duct carcinoma, adenosquamous carcinoma, acinic cell carcinoma, and Warthin tumor are negative for the MAML2 rearrangements.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Reliable results are dependent on adequate specimen collection and processing. This test has been validated on formalin-fixed, paraffin-embedded tissue; other types of fixatives are discouraged. Improper treatment of tissues, such as decalcification, may cause FISH failure.
Clinical diagnosis and/or therapy should not be based solely on this assay. The results should be considered in conjunction with clinical information and/or additional diagnostic tests.
A blinded investigation was performed on 28 MEC and 51 control tissues. All samples were identified and diagnosed by a soft tissue pathology expert. Two technologists scored 100 cells each. The MAML2 locus was found to be rearranged in 26 of 28 MEC cases (93%) and 0 of 51 control cases.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Stewart FW, Foote FW, Becker WF: Mucoepidermoid tumors of salivary glands. Ann Surg 1945;122:820-844
2. Spiro RH, Huvos AG, Berk R, Strong EW: Mucoepidermoid carcinoma of salivary gland origin. A clinicopathologic study of 367 cases. Am J Surg 1978;136:461-468
3. Seethala RR, Dacic S, Cieply K, et al: A reappraisal of the MECT1/MAML2 translocation in salivary mucoepidermoid carcinomas. Am J Surg Pathol 2010 Aug;34(8):1106-1121
4. Behboudi A, Enlund F, Winnes M, et al: Molecular classification of mucoepidermoid carcinomas-prognostic significance of the MECT1-MAML2 fusion oncogene. Genes Chromosomes Cancer 2006 May;45(5):470-481