[1127] Fluorescent In-Situ Hybridization for Detection of MAML2 Rearrangements in Oncocytic Mucoepidermoid Carcinomas: Utility as a Diagnostic Test

JJ Garcia, JL Hunt, I Weinreb, JB McHugh, EL Barnes, K Cieply, S Dacic, RR Seethala. University of Pittsburgh, Pittsburgh, PA; Cleveland Clinic, Cleveland, OH; University Health Network and University of Toronto, Toronto, ON, Canada; University of Michigan, Ann Arbor, MI

Background: Oncocytic mucoepidermoid carcinoma (OMEC) poses diagnostic challenge because of its overlap with other oncocytic salivary gland lesions, including Warthin's tumor (WT) when there is a prominent lymphoid stroma. While the prognostic value of the t(11;19) MECT1-MAML2 fusion gene has been established in MEC, its potential use to discriminate OMEC from other mimics has not been established.
Design: Eleven cases of OMEC were selected and categorized based on predominant growth pattern: solid, cystic, or Warthin-like (defined by prominent lymphoid stroma). Available clinical and pathologic parameters, including grade were obtained. Cases were evaluated for MAML2 rearrangements by fluorescent in-situ hybridization (FISH) using a MAML2 - 11q21 break apart probe (SpectrumGreen-labeled BAC probe RP11-676L3 and SpectrumOrange-labeled BAC probe RP11-16K5; Children's Hospital Oakland Research Institute, Oakland, CA, USA) spanning the entire chromosome region of the MAML2 gene. At least 60 interphase tumor cell nuclei were evaluated per case. A minimum of 20% of cells with split signal was considered positive.
Results: All OMEC were parotid tumors with a median age of 55.3 years (range: 9-83) and a female to male ratio of 2.7:1. Grade distribution was as follows: low-grade - 5, intermediate-grade - 3, and high-grade - 3. The histologic patterns observed were: solid - 5, cystic - 3, Warthin-like - 2, and mixed solid/Warthin-like - 1. Seven of the 11 cases (64%) showed a MAML2 rearrangement by FISH. No direct correlation was seen between rearrangement status and histologic grade or growth pattern.
Conclusions: MAML2 rearrangement is frequently detected by FISH in OMEC and is a potentially useful diagnostic tool in discriminating OMEC from other oncocytic lesions.
Category: Head & Neck

Monday, March 9, 2009 1:00 PM

Poster Session II # 160, Monday Afternoon