Chest radiography was performed for a 7-year-old girl with persistent cough and fever who was unresponsive to oral antibiotics and showed loss of volume of left lung sustained by almost total atelectasis. The patient was then admitted to the pediatric ward to begin intravenous antibiotic therapy. Serological tests for Chlamydia pneumoniae , Mycoplasma pneumoniae , and QuantiFERON test for tuberculosis were negative. A computed tomography (CT) scan showed an extended mass that occupied the entire upper lobe with axial dimensions of 70 x 47 mm and assumed discreet enhancement in all the study phases. The bronchi for the upper lobe were no longer patent with endobronchial projection affecting the middle third of the main left bronchus. The mass caused posterior dislocation of the pulmonary arterial vascular axis and inferior dislocation of the superior pulmonary vein. Based on the radiological reports, the patient was referred to our pediatric surgery unit. To better define the characteristics of the lesion, a magnetic resonance imaging was performed. The pictures confirmed the presence of an expansive pulmonary lesion with a probable origin from the upper left lobe with transverse diameters of 57 x 45 mm and longitudinal extension of 85 mm. The lesion infiltrated the pulmonary hilum and invaded the bronchial structures up to the left main bronchus ~2 cm from the carina. It appeared adherent to the common trunk of the pulmonary artery and to the pericardium at the level of the left atrium and ventricle with infiltration of the superior pulmonary vein. The mass appeared to be surrounded by a thin rim of consolidated lung parenchyma; therefore, it does not seem to infiltrate the thoracic wall ( Fig. 1 ). For a complete diagnostic work-up, positron emission tomography-CT was performed; the findings showed softened uptake of the tracer at the voluminous expansive formation that tended to accentuate along the margins. Echocardiography revealed a 7-mm ostium secundum atrial defect with left to right shunt and deformity of the left ventricular cavity, with preserved systolic function. The deformity was attributable to the mass. All the tumor markers were negative. After multidisciplinary evaluation, ultrasonography-guided transthoracic core needle biopsy (22 Gauge) and bronchoscopic biopsies were performed to establish the diagnosis. Histopathologic examinations revealed the presence of medium-small-sized cells neoplasia, ovoid and plasmacytoid, with eosinophilic cytoplasm, lacking of evident cytological atypia with solid growth or in large nests alternating with myxoid and dense collagenous stroma. Immunohistochemical reactivity was positive for cytokeratine (CK) AE1AE3, p63, epithelial membrane antigen (EMA), S100, beta-catenin, SOX10, and terminal deoxynucleotidyl transferase (TDT). The morphological and immunophenotypic data were more suggestive of myoepithelioma. However, the immunocytochemical expression of TdT did not exclude the possibility of thymic neoplasm. Fluorescence in situ hybridization analysis showed the absence of translocation of FUS gene in 16p11, EWS gene in 22q12, and SS18 gene in 18q11.2. The case was discussed among pediatric surgeons, oncologists, and radiologists who concluded that the nature of the cancer was not sensitive to neoadjuvant treatment, thus indicating elective radical surgery. 
 After the performance of sternotomy and opening of the pleura bilaterally, the left thoracic mass was revealed. The mass infiltrated the entire left lung and was attached to and infiltrated the pericardium, the left pulmonary artery and veins, as well as the left bronchus. We proceeded to release the left lower lobe by making selective distal ligation of the pulmonary arterial and venous vessels and of the left lobar bronchus. The lobectomy was completed with a mechanical stapler. The lower lobe appeared infiltrated by the mass at the level of the fissure. After resecting the lingular lobe, it was necessary to proceed under extracorporeal circulation to isolate the left pulmonary artery and veins. We isolated the pulmonary artery trunk as well as tied and dissected the Botallo's duct and the left branch of the pulmonary artery. The two left pulmonary veins and the main left bronchus were dissected and sutured. The mass was isolated from the remaining pericardium, from the vagus nerve, and from the phrenic nerve. Once the left pneumonectomy was completed and hemostasis was achieved, the interatrial defect was surgically closed, and a temporary pacemaker was implanted. A thoracic expander of 11 x 6 cm was applied and filled with 100 mL of saline solution. The expander reservoir connector was placed outside of the chest wall, and the reservoir was placed in a subcutaneous pocket. A left thoracic drain was placed dorsal to the expander. The postoperative course was uneventful. The temporary pacemaker was removed after 5 days, and the drain was removed after 8 days. The expander was gradually filled up to 200 mL with saline in three different infusions over 3 weeks ( Fig. 2 ). The patient was discharged on postoperative day 18. Histopathological analysis confirmed the presence of primary myoepithelial carcinoma of the lung (PMC-L) that infiltrated the bronchial wall up to the mucosa, the peribronchial fibroadipose tissue with vascular perineural-neural invasion, the pulmonary parenchyma, the visceral pleura, the pericardium, and a peribronchial lymph node with embolic metastasis. In view of the rarity of this neoplasm, the TREP group ("Rare Tumors in Pediatric Age") means rare tumors in pediatric age group was consulted to set up a plan for the follow-up care. The patient was then subjected to radiotherapy with rapid arc technique on the left thoracic wall in 34 diaphragmatic thickening fractions, 61.2 Gy in total. At the 14-month follow-up, the patient was alive and was breathing normally without oxygen support. Neither recurrence of PMC-L nor metastasis occurred, and no chest deformities were observed.