Case report: diagnostic challenges and long-term survival of a child with bronchial mucoepidermoid carcinoma

Bronchial mucoepidermoid carcinoma (MEC) is a rare pediatric malignant neoplasm of difficult diagnosis. We report on the case of a 15-year-old patient who presented with cough, fever, left chest pain, and difficulty breathing. A chest computed tomography (CT) scan revealed collapse of the left lung with a solid mass with poorly defined margins located close to the left lung hilum, and another smaller enhancing solid nodule located adjacent to the aortic arch. Biopsy of the lesion revealed a malignant epithelial neoplasm with clear cell morphology, overexpression of TFE3 by immunohistochemistry (IHC), but without TFE3 rearrangement by fluorescence in situ hybridization (FISH) analysis. Transcriptome [RNA sequencing (RNA-seq)] analysis of the specimen was positive for CRTC3::MAML2 fusion transcript, and a diagnosis of bronchial MEC was made. The patient received three courses of PLADO (cisplatin and doxorubicin) and three surgeries to remove the tumor completely and is currently in remission for 5 years off therapy. Clinical presentation of bronchial MEC is similar to that of other pulmonary neoplasms. In our challenging case, the identification of CRTC3::MAML2 fusion was essential for diagnosis. The successful outcome in this case was made possible by the coordinated efforts of multiple specialties and close consultation for advanced molecular tests.