ADULT PULMONARY BLASTOMA: A TALE OF TWO HISTOLOGIES

Abstract

INTRODUCTION: Pulmonary blastoma is a rare tumor with histological similarity to fetal lung tissue. Comprising less than 0.5% of all malignant pulmonary neoplasms, approximately 200 case reports have been described in the literature. The classic biphasic pulmonary blastoma found in adults, consists of a malignant glandular component and a mesenchymal component that are both embryonal in appearance. This case report reviews the clinical, radiographic and pathologic findings in a 45 year old male diagnosed with classic biphasic pulmonary blastoma. CASE PRESENTATION: A 45 year old male with no previously diagnosed medical history presented to the clinic with complaints of shortness of breath, cough and exertional dyspnea. These symptoms occured over a 3 month time period, and he had never experienced these symptoms before. He described the cough as constant and non-productive, with no hemoptysis. He had not experienced fevers, weight loss, wheezing or chest pain during this time period. He is a current tobacco user and has a 40 pack year history of smoking. He has no known chemical or occupational exposures. A routine evaluation was initiated, which included basic blood laboratories and a chest radiograph. A mass was then discovered and he was referred for CT guided biopsy. Histologic examination revealed mesenchymal tissue and malignant glands with an embryonal appearance. Classic biphasic pulmonary blastoma was diagnosed based on pathology. He was subsequently referred to a cardiothoracic surgeon for resection. DISCUSSIONS: Pulmonary blastomas contain immature cellular components. The term blastoma has been used to describe tumors in both children and adults. Pulmonary blastoma has been subdivided into histologically characteristic groups: classic biphasic pulmonary blastoma, well-differentiated fetal adenocarcinoma and pleuropulmonary blastoma of childhood. Classic biphasic pulmonary blastoma contains malignant glands and mesenchymal tissue that are both embryonal in appearance. A welldifferentiated fetal adenocarcinoma contains malignant glands and benign appearing mesenchymal tissue. A pleuropulmonary blastoma contains malignant glands of embryonal appearance and benign appearing epithelium. Patients with pulmonary blastoma can present asymptomatically with an incidental finding of a lung mass on chest radiography. Common symptoms include cough, hemoptysis, dyspnea, and chest pain. Symptoms such as fever, weight loss, and recurrent pneumonia may also present. Prognosis of pulmonary blastoma is poor, with a reported survival of 17% at 5 years. The primary treatment options include surgery and chemotherapy. Complete surgical resection in early presentation is regarded as the best treatment option. Surgical resection, however, is marred by large tumor size and frequent postoperative recurrence. In patients with inoperable disease, chemotherapy has been used with varying degrees of success. More studies are needed as no standardized chemotherapeutic regimen exists at this time, and it is unclear if radiotherapy is helpful. CONCLUSION: Pulmonary blastoma is a rare neoplasm affecting very few adults. Symptoms are nonspecific and most are incidentally discovered on routine radiography. There are no clearly defined treatment regimens, although complete surgical resection appears to confer the best prognosis. More trials are necessary to determine the most effective and appropriate therapies.