Bronchial mucoepidermoid carcinoma – A challenging diagnosis on biopsy

Bronchial mucoepidermoid carcinoma (MEC) is a rare malignant tumor. The clinical, radiological, and bronchoscopic features are nonspecific. We report this case to highlight the overlapping immunohistochemical findings and the challenges of diagnosing this rare tumor on biopsy. The immunohistochemical features may overlap with that of squamous cell carcinoma. We present the case of a 30-year-old woman who presented with cough and fever. Radiological evaluation showed consolidation. Bronchoscopy showed a mass which on biopsy showed bland looking cells mimicking carcinoid. The immunohistochemical evaluation showed positivity for p40 and cytokeratin 5/6 which was misleading. A final diagnosis of MEC was made which explained the immunohistochemical findings. The diagnosis of bronchial MEC on biopsy may be challenging due to the other close differentials and its rarity. The awareness of its histopathological and immunohistochemical features along with a high index of suspicion will help in arriving at a correct diagnosis on biopsy. The pathologist and the clinician should be aware of this entity.