title: Thymic Mucoepidermoid Carcinoma: Report of a Case With CTRC1/3-MALM2 Molecular Studies.
abstract: Thymic mucoepidermoid carcinoma (TMEC) is a vanishingly rare entity that usually presents as low to intermediate grade MEC and carries a better prognosis when compared with other poorly differentiated thymic carcinomas. The recently described fusions, t(11;19)(q21;p13) CREB (cAMP response element-binding protein)-regulated transcription coactivator 1 and MAML2, mastermind-like gene 2 (CRTC1-MAML2) and t(11:15)(q21;q26) CRTC3-MAML2 characterize a considerable proportion of MEC examples arising from a variety of anatomical sites. Recent data point out that the aberrant proteins produced by this fusion drive oncogenesis by disrupting the cAMP/CREB and NOTCH1 pathways. To date, only 2 TMEC cases have been reported to have MAML2 rearrangements, a feature that was found to be absent in TMEC mimics. These findings led the authors to recommend this test as a diagnostic tool in the differential diagnosis for thymic carcinoma. Herein, we present a case of TMEC arising in a 58-year-old woman, which was predominantly cystic with intracystic papillary formations composed of a mixture of mucinous cells and intermediate/epidermoid eosinophilic cells. This case was negative for CTCR1-MAML2 and CTCR3-MAML2 fusion transcripts by reverse transcriptase polymerase chain reaction and lacked a MAML2 rearrangement by fluorescence in situ hybridization. We report a CTCR1/3-MAML2 fusion and MAML2 rearrangement-negative TMEC, indicating that a different molecular pathway must be involved in the generation of these tumors. The possibility of fusion-negative TMEC should be taken into consideration in the differential diagnosis of a thymic carcinoma.
authors.affiliation: Moffitt Cancer Center, Tampa, FL, USA carlos.prietogranada@moffitt.org.
authors.forename: Carlos N
authors.initials: CN
authors.lastname: Prieto-Granada
authors.affiliation: Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inagaki
authors.affiliation: Baystate Medical Center-Tufts University School of Medicine, Springfield, MA, USA.
authors.forename: James
authors.initials: J
authors.lastname: Mueller
mesh_terms: D018277:Carcinoma, Mucoepidermoid / Q000235:genetics* / Q000473:pathology*; D002918:Chymotrypsin / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008875:Middle Aged; D009687:Nuclear Proteins / Q000235:genetics; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013953:Thymus Neoplasms / Q000235:genetics* / Q000473:pathology*; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; C471297:MAML2 protein, human; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D015534:Trans-Activators; D014157:Transcription Factors; D002918:Chymotrypsin; C117569:chymotrypsin C
keywords: CRTC1-MAML2; CRTC3-MAML2; fluorescence in situ hybridization; reverse transcriptase polymerase chain reaction; thymic mucoepidermoid carcinoma