Primary Epithelial Myoepithelial Lung Carcinoma
A 51-year-old female was admitted to the hospital with an abnormal chest radiographic finding on a periodic medical inspection. The patient was a non-smoker, and her past medical history was unremarkable. She did not have any respiratory symptoms, such as cough, hemoptysis, dyspnea, fever, or pneumonia. There were no palpable adenopathies, and cardiopulmonary auscultation and laboratory study results, including an electrocardiogram and blood analysis, were within reference limits. A chest radiograph showed a mass 3.2×2.8 cm in size in the left peripheral lung field. A chest computed tomography (CT) scan revealed a well-defined mass of 3×2.9 cm that bordered the visceral pleura at the lingular segment of the left upper lobe (LUL) (). A percutaneous needle biopsy was performed, and the diagnosis indicated that the mass was a salivary gland tumor. Positron emission tomography (PET)-CT revealed a LUL mass with a maximal standardized uptake value of 3.2 and uptake, which indicated distant metastasis. The patient was treated by a lobectomy of the left upper lung with lymph node dissection via video-assisted thoracic surgery. Grossly, the excised section of the left upper lung showed a well-circumscribed, gray-white to yellow tumor mass, measuring 3.3×2.4×1.9 cm (). A microscopic examination revealed that the cut section of the tumor was composed of two types of cells: tubular and glandular structures filled with eosinophilic material, mixed with solid spindle and polygonal cell areas (H&E, ×200). The inner tubular layer showed epithelial cell characteristics, whereas the outer layer exhibited myoepithelial cell characteristics. A few mitotic figures were also seen (H&E, ×400) (). Immunochemical staining for epithelial membrane antigen was positive in the inner tubular layers and epithelial components (EMA, ×200). Immunostaining for actin was positive in the outer tubular layer and solid areas (Actin, ×200). Immunostaining for S-100 showed a focal positive reaction in the outer tubular layer and solid areas (S-100, ×200) (). The postoperative tumor-node-metastasis (TNM) stage was T2aN0M0, and the pathologic stage was Ib. The patient did not receive any adjuvant treatment and was followed up for 16 months without any local recurrence or distant metastasis.