Thymic Mucoepidermoid Carcinoma: Report of a Case With CTRC1/3-MALM2 Molecular Studies. (June 2015)

• Record Type: Journal Article
• Authors: Prieto-Granada, Carlos N.; Inagaki, Hiroshi; Mueller, James
• Is Part Of: International journal of surgical pathology. Volume 23:Number 4(2015)
• Page Start: 277
• Page End: 283
• Publication Date: 2015-06
• Subjects: thymic mucoepidermoid carcinoma -- CRTC1-MAML2 -- CRTC3-MAML2 -- reverse transcriptase polymerase chain reaction -- fluorescence in situ hybridization; Pathology, Surgical -- Periodicals; 617.07
• DOI: 10.1177/1066896915576959
• Languages: English
• ISSNs: 1066-8969

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.