CASE REPORT article
Front. Oncol.
Sec. Thoracic Oncology
Volume 15 - 2025 | doi: 10.3389/fonc.2025.1578256
Primary pulmonary mucoepidermoid carcinoma lacking squamous differentiation with concurrent CRTC1::MAML2 fusion and EWSR1 gene alteration: a case report and literature review
Provisionally accepted
- 1Department of Pathology, Nanfang Hospital, Southern Medical University, Guangzhou, China
- 2Guangdong Provincial Key Laboratory of Molecular Tumor Pathology, Southern Medical University, Guangzhou, China
- 3Department of Pathology, School of Basic Medicine, Southern Medical University, Guangzhou, China
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Primary pulmonary mucoepidermoid carcinoma (PMEC) is a rare lung malignancy mostly harboring the CRTC1/3::MAML2 fusion. We reported a 25-year-old female with refractory respiratory symptoms unresponsive to anti-infective therapy. Imaging suggested a solid nodule in the left central lung invading left main bronchus and the adjacent left lower lobe. The patient underwent left lower lobe sleeve resection. Microscopically, the tumor cells were arranged into glandular and papillary structures composed of clear and oncocytic cells with mild atypia, accompanied by intraluminal eosinophilic colloid-like material, focal scattered mucus-secreting cells and mucus extravasation. Immunohistochemical analysis revealed positivity for pan-epithelial markers but negativity for squamous differentiation markers such as p63, p40 and CK5/6. Fluorescence in situ hybridization (FISH) identified MAML2 and EWSR1 gene rearrangements, while RNA-sequencing confirmed the CRTC1::MAML2 fusion without identifying a transcriptional partner for EWSR1. This report expands the clinicopathological and molecular spectrum of PMEC, underscoring the diagnostic utility of MAML2 rearrangement analysis in distinguishing between primary PMEC lack of squamous differentiation and other central lung tumors.
Keywords: Primary pulmonary mucoepidermoid carcinoma, Salivary gland-type tumor, MAML2, EWSR1, case report
Received: 17 Feb 2025; Accepted: 10 Jul 2025.
Copyright: © 2025 Wang, Yu, Li and Lin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Jie Lin, Department of Pathology, Nanfang Hospital, Southern Medical University, Guangzhou, China
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