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

Mod Pathol. 2009 Dec;22(12):1575-81. doi: 10.1038/modpathol.2009.126. Epub 2009 Sep 11.

Abstract

Mucoepidermoid carcinoma is the most common primary malignancy of the salivary gland. We and others showed that CRTC1-MAML2 gene fusion was associated with favorable clinicopathological tumor features. Recently, a novel gene fusion, CRTC3-MAML2, was reported as a rare gene alteration in a case of mucoepidermoid carcinoma. However, its frequency and clinicopathological significance remains unclear. In all, 101 cases of mucoepidermoid carcinoma and 89 cases of non-mucoepidermoid carcinoma of the salivary gland were analyzed, and RNA was extracted from formalin-fixed, paraffin-embedded specimens. In the CRTC family, there have been three genes, CRTC1, CRTC2, and CRTC3. We developed reverse transcription-polymerase chain reaction (RT-PCR) assays for CRTC1-MAML2, CRTC2-MAML2, and CRTC3-MAML2 fusions. Clinicopathological data of the patients were obtained from their clinical records. Of 101 cases of mucoepidermoid carcinoma, 34 (34%) and 6 (6%) were positive for CRTC1-MAML2 and CRTC3-MAML2 fusion transcripts. However, in the 89 cases of non-mucoepidermoid carcinoma, neither transcript was noted. In the former cases, CRTC1-MAML2 and CRTC3-MAML2 fusions were mutually exclusive. The other fusion, CRTC2-MAML2, was not detected. We confirmed that the clinicopathological features of CRTC1-MAML2-positive mucoepidermoid carcinomas indicated an indolent course. CRTC3-MAML2-positive mucoepidermoid carcinomas also had clinicopathologically favorable features; all cases showed a less advanced clinical stage, negative nodal metastasis, no high-grade tumor histology, and no recurrence or tumor-related death after surgical resection of the tumor. It is interesting to note that patients with CRTC3-MAML2-positive tumors (mean 36 years of age) were significantly younger that those with the CRTC1-MAML2 fusion (55 years) and those with fusion-negative tumors (58 years). In conclusion, CRTC3-MAML2 fusion, which is mutually exclusive with CRTC1-MAML2 fusion and specific to mucoepidermoid carcinoma, may be detected more frequently than previously expected. Mucoepidermoid carcinomas possessing CRTC3-MAML2 fusion may be associated with favorable clinicopathological features and patients may be younger than those with CRTC1-MAML2 fusion or those with no detectable gene fusion.

MeSH terms

  • Adult
  • Age Factors
  • Carcinoma, Mucoepidermoid / genetics*
  • Carcinoma, Mucoepidermoid / mortality
  • Carcinoma, Mucoepidermoid / pathology
  • Carcinoma, Mucoepidermoid / surgery
  • DNA-Binding Proteins / genetics*
  • Disease-Free Survival
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Gene Fusion*
  • Humans
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • Neoplasm Staging
  • Nuclear Proteins / genetics*
  • RNA, Messenger / analysis*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Salivary Gland Neoplasms / genetics*
  • Salivary Gland Neoplasms / mortality
  • Salivary Gland Neoplasms / pathology
  • Salivary Gland Neoplasms / surgery
  • Time Factors
  • Trans-Activators
  • Transcription Factors / genetics*
  • Treatment Outcome
  • Young Adult

Substances

  • CRTC1 protein, human
  • CRTC2 protein, human
  • CRTC3 protein, human
  • DNA-Binding Proteins
  • MAML2 protein, human
  • Nuclear Proteins
  • RNA, Messenger
  • Trans-Activators
  • Transcription Factors