Oncocytic mucoepidermoid carcinoma of the parotid gland with CRTC1-MAML2 fusion transcript: report of a case with review of literature.

Oncocytic mucoepidermoid carcinoma is a very rare variant of mucoepidermoid carcinoma, composed predominantly of oncocytic cells. Most previously reported cases described the difficulty in histologic differentiation from other oncocytic tumors. Here we report a case of oncocytic mucoepidermoid carcinoma of parotid gland diagnosed by the detection of CRTC1-MAML2 fusion. A 53-year-old man had a left superficial parotidectomy conducted for 3-cm-sized mass. The resected tumor was composed almost exclusively of oncocytic tumor cells. With detailed histologic evaluation, scarce vacuolated tumor cells, suggestive of mucous cell of mucoepidermoid carcinoma, and one focus of tumor embolism in a vein were found, suggesting the possibility of oncocytic mucoepidermoid carcinoma. Immunohistochemically, oncocytic cells were diffusely positive for p63. Reverse transcriptase polymerase chain reaction and direct sequencing revealed CRTC1-MAML2 translocation of this tumor. To our knowledge, this report describes the first case of oncocytic mucoepidermoid carcinoma confirmed with CRTC1-MAML2 fusion. Identification of this fusion gene may help in distinguishing oncocytic mucoepidermoid carcinoma from its mimics.

Fujimaki M ，Fukumura Y ，Saito T ，Mitani K ，Uchida S ，Yokoyama J ，Yao T ，Ikeda K ... -  《-》

Fluorescence in situ hybridization for detection of MAML2 rearrangements in oncocytic mucoepidermoid carcinomas: utility as a diagnostic test.

Oncocytic mucoepidermoid carcinoma poses diagnostic challenge because of its histologic overlap with other oncocytic salivary gland lesions, including Warthin tumor. Although the prognostic value of the t(11;19) MECT1-MAML2 fusion gene has been established in mucoepidermoid carcinoma, its diagnostic use in discriminating oncocytic mucoepidermoid carcinoma from histologic mimics is unexplored. We evaluated the translocation status in 14 cases of oncocytic mucoepidermoid carcinoma using a MAML2-11q21 break-apart probe spanning the entire chromosome region of the MAML2 gene and correlated these findings with clinicopathologic parameters including age, sex, stage, predominant growth pattern, grade, and p63 immunostaining pattern. All oncocytic mucoepidermoid carcinomas were parotid tumors with a mean patient age of 54.6 years (range, 9-85) and a female to male ratio of 5:2. Grade distribution was as follows: low grade, 9; intermediate grade, 2; and high grade, 3. The histologic patterns observed were as follows: solid, 4; cystic, 8 (of these, 5 had Warthin-like lymphoid stroma); and mixed, 2. Solid oncocytic mucoepidermoid carcinomas showed a diffuse p63 staining pattern, whereas cystic oncocytic mucoepidermoid carcinomas showed staining of the outer layer of intermediate cells ranging from a bilayer to areas of complex multilayering and plaque-like proliferation. Ten (71%) of the 14 cases showed a MAML2 rearrangement by fluorescence in situ hybridization. No correlation was seen between rearrangement status and histologic grade, growth pattern, or p63 staining pattern. However, we demonstrate that the presence of MAML2 rearrangement can be used as supportive evidence to distinguish oncocytic mucoepidermoid carcinoma from other oncocytic lesions.

García JJ ，Hunt JL ，Weinreb I ，McHugh JB ，Barnes EL ，Cieply K ，Dacic S ，Seethala RR ... -  《-》

Clinicopathological significance of the CRTC3-MAML2 fusion transcript in mucoepidermoid carcinoma.

Nakayama T ，Miyabe S ，Okabe M ，Sakuma H ，Ijichi K ，Hasegawa Y ，Nagatsuka H ，Shimozato K ，Inagaki H ... -  《-》

t(11;19) translocation and CRTC1-MAML2 fusion oncogene in mucoepidermoid carcinoma.

O'Neill ID 《-》

CRTC1 rearrangements in the absence of t(11;19) in primary cutaneous mucoepidermoid carcinoma.

Lennerz JK ，Perry A ，Dehner LP ，Pfeifer JD ，Lind AC ... -  《-》