A RARE FORM OF SYNCHRONOUS LUNG CANCER: MUCOEPIDERMOID CARCINOMA

Abstract

TOPIC: Lung Cancer TYPE: Medical Student/Resident Case Reports INTRODUCTION: We report a unique case of lung cancer involving two different histologic variants. Mucoepidermoid carcinoma (MEC) a salivary gland-type tumor and conventional adenocarcinoma CASE PRESENTATION: The patient in this case study is a 57-year-old male non-smoker with history of hypertension, prostate cancer and deep venous thrombosis, who was incidentally found to have chest x-ray findings concerning for diaphragmatic eventration. Computed tomography (CT) of the chest revealed a linear area of scarring in the left upper lobe and a 5 mm nodule in the left lower lobe (Figure 1, 2). Positron emission tomography-CT (PET-CT) was obtained to evaluate the nodule which revealed a metabolically active 2.8 x 1.5 cm opacity in the left upper lobe, suspicious for malignancy (Figure 3). He underwent CT guided biopsy of the left upper lobe nodule. After the diagnosis, he underwent left Video-Assisted Thoracic Surgery which converted into an open thoracotomy with left upper lobe lobectomy. Microscopic examination revealed that the tumor was located in the peribronchial area of the lung and compromised of two different histologic components: A central MEC component, containing mucin producing cells. The MEC part was negative for cytokeratin 7 (CK7), thyroid transcription factor-1 (TTF-1) and Napsin. The central MEC part of the tumor is surrounded by adenocarcinoma component. The adenocarcinoma component presented with mixed lepidic and acinar patterns positive for TTF-1, Napsin and CK7 but negative for P63 and P40 stains. According to the seventh edition of TNM staging for lung tumors, the clinical stage of this patient was pT2aNO Stage IV. DISCUSSION: Salivary gland-type lung cancers are relatively rare neoplasms of the lung. They represent about 0.1 to 0.2% of primary lung tumors and are detected incidentally. CT findings usually include a well-defined endobronchial mass with or without obstructive pneumonia or atelectasis (1). The genetic analysis of cancer cells is the standard of care in order to select the most effective therapy; however, the genetic characteristics of MEC are not yet fully understood. Mutations in EGFR and ALK genes are routinely tested to identify lung adenocarcinoma patients who could benefit from treatment with target therapies. Treatment of choice is complete surgical excision as its controversial if pulmonary MEC is responsive to chemotherapy and radiotherapy; however, in cases of high-grade PMEC, adjuvant chemotherapy has been reserved when complete resection is impossible. Patients with unresectable disease have responded to EGFR-targeted therapy. CONCLUSIONS: This case report serves to illustrate the rare combination of MEC and adenocarcinoma. Early surgical intervention has shown to be favorable in low-grade MEC; however, further investigation is required to evaluate for the need for adjunct therapy in the future given the risks of developing high-grade MEC and adenocarcinoma. REFERENCE #1: Li X, Zhang W, Wu X, et al. Mucoepidermoid carcinoma of the lung: common findings and unusual appearances on CT. Clin Imaging. 2012;36:8–13. REFERENCE #2: Yousem, S.A. and Hochholzer, L. (1987), Mucoepidermoid tumors of the lung. Cancer, 60: 1346-1352. https://doi.org/10.1002/1097-0142(19870915)60:6<1346::AID-CNCR2820600631>3.0.CO;2-0 REFERENCE #3: Leonardi HK, Jung-Legg Y, Legg MA, Neptune WB. Tracheobronchial mucoepidermoid carcinoma. Clinicopathological features and results of treatment. J Thorac Cardiovasc Surg. 1978;76(4):431–8. DISCLOSURES: No relevant relationships by Chandan Buttar, source=Web Response No relevant relationships by Debra Ferman, source=Web Response No relevant relationships by Sofia Lakhdar, source=Web Response No relevant relationships by Theo Trandafirescu, source=Web Response