High-grade Pulmonary Mucoepidermoid Carcinoma in a Child: A Rare Case Report

Mucoepidermoid Carcinoma (MEC) of the lung is a rare salivary gland-type tumour, accounting for <1% of primary pulmonary neoplasms, with female predominance in some series and a wide age range. This case reports a four-year-old girl with a four-month history of cough, haemoptysis, and breathlessness. Imaging revealed a 3.2×1.5×2.5 cm enhancing polypoidal mass arising from the left main bronchus, extending into the carina and lower trachea, with mediastinal shift and bronchiectatic changes. The patient underwent pneumonectomy and the histology showed Squamous metaplasia without dysplasia beneath that showed a neoplasm was composed predominantly of squamoid and intermediate cells, with cystic spaces lined by mucin-secreting cells and focal necrosis. Immunohistochemistry showed Tumour protein (p63) positivity in intermediate cells. Based on the Armed Forces Institute of Pathology (AFIP) and Memorial Sloan Kettering Cancer Center (MSKCC) grading systems, the diagnosis of high-grade MEC was confirmed. MEC involves the CREB Regulated Transcription Coactivator 1 (CRCT1 formerly known as MECT1) and Mastermind Like Transcriptional Coactivator 2 (MAML2) genes, located on chromosomes 19p13 and 11q21, respectively. Epidermal Growth Factor Receptor (EGFR) overexpression, observed in salivary gland MEC, is more sensitive to gefitinib than other wild-type EGFR non-small cell lung cancer cell lines and may offer potential for targeted therapy, though its role in pulmonary MEC remains uncertain. Each case of pulmonary MEC is inherently novel due to its rarity, presentation and histopathological diversity. Sharing these findings is essential for helping clinicians navigate diagnostic challenges, refine protocols, and predict patient outcomes for these uncommon lung tumours. Prognostic factors include histological grade, tumour, node, metastasis (TNM) stage, resection status, nodal metastasis, and patient age. Recognition of its molecular profile may guide future targeted therapies.