Pulmonary blastoma(PB) is a rare primary non-small cell lung cancer(NSCLC) that is composed of both malignant glands and mesenchyme that are primitive/embryonal in appearence. It involves less than 1% of all lung cancers with a frequency about 0.25-0.5%1.
This is a case of a 57 year-old female that presented as an outpatient referral for an abnormal chest x-ray(CXR) during pre-operative surgical clearence for knee arthroscopy. She was asymptomatic at presentation with no history of tuberculosis exposure or previous pneumonia. She has a history of asthma/bronchitis requiring bronchodilator therapy and infrequent courses of oral steroids. There was a remote history of smoking tobacco for a year during her teens, otherwise social, occupational, and family history were unremarkable. Physical examination and laboratory values were normal.CT revealed a 2.2-cm enhancing soft-tissue mass in the apex of the RUL with no evidence of mediastinal or pleural disease present. Pulmonary function testing showed a mild obstructive ventilatory defect with significant reversibility, FEV1 of 1.84- 68% of predicted. A whole body positive emission tomography scan(PET) was negative- no focal area of abnormal radionuclide uptake suggesting a benign process. She had a RUL lobectomy performed for possible curative treatment without any complications. Pathological examination of the specimen was positive for biphasic PB. The surgical margins were clear, and 8 regional lymph nodes were negative for metastasis. The tumor measured 2.8-cm in diameter (well-circumscribed, firm, rubbery mass). Follow-up, currently, involves serial CXR’s every 3 months with a chest CT every 12 months depending on the results of the CXR’s.DISCUSSION: PB is a rare NSCLC which morphologically resembles fetal lung structure. It is subdivided into 2 categories: classic biphasic PB and well-differentiated fetal adenocarcinoma2. They may occur at any age, but biphasic PB tends to occur between 35-40 years of age3. There is usually a history of tobacco use with common symptoms of hemoptysis, cough, and fever. 25-40% of cases are asymptomatic, usually an incidental finding4. There maybe pleuritic chest pain associated with pleural effusions5. Radiographic findings are usually a well-demarcated, peripheral lesion favoring upper lobes. It can be large, averaging 10-cm (2.5-25-cm)2 with a rapid growth curve. Biphasic PB has a worse prognosis when compared to fetal adenocarcinoma due to its higher incidence of metastasis with a survival comparable to common NSCLC’s. The treatment is similar as well. Surgical resection is the treatment of choice. There are no other therapeutic or adjuvant guidelines which exist6.
PET is an accurate, noninvasive means for diagnosis of pulmonary nodules and larger mass lesions7. PB can present as a pulmonary nodule. In this case of PB, it was a false-negative result via PET. The lung cancers that are known in literature to cause a false-negative PET are broncho-alveolar carcinoma and carcinoid tumors.
Posteroanterior(top) and lateral(bottom) CXR’s demonstrating an approximately 2-cm RUL nodule.
Chest-CT characterizing RUL lesion, mediastinal(top) and lung(bottom) windows.
Low(top) and high(bottom) power magnification of the RUL specimen.
T.M. Henderson, None.