Challenges in diagnosis of pulmonary mucoepidermoid carcinoma: A case report

RATIONALE: Pulmonary mucoepidermoid carcinomas (PMECs) of the lung are rare malignant tumors. Despite progresses in examinations, the tumor represents a diagnostic challenge for pathologists and clinical physicians. Here, we present a patient who was eventually diagnosed with PMEC by the bronchoscopic examinations conducted three times. PATIENT CONCERNS: We present the case of a 41-year-old female who was initially diagnosed with pulmonary pleomorphic adenoma (PPA) with a 68 × 82 mm mass and nodules in her lung and eventually diagnosed with PMEC. DIAGNOSES: Based on histopathology, immunohistology, and imaging studies, the patient was diagnosed with PMEC (pT4N2M1). INTERVENTIONS: The patient received first-line systemic chemotherapy regime (gemcitabine combined with carboplatin). OUTCOMES: The patient received 2 cycles of chemotherapy. Based on the response evaluation criteria in solid tumor, she achieved partial response, and the mass was distinctly decreased from 68 × 22 mm to 41 × 17 mm. LESSONS: This case presents a rare PMEC overlapping with PPA, based on histological findings, suggesting that besides imaging studies and laboratory examinations, multiple biopsies and ThinPrep cytology tests are necessary to obtain an accurate diagnosis. The patient showed positive response to chemotherapy.