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Pulmonary Blastoma: A Case Report

Howard University, Silver Spring, MD

INTRODUCTION: 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.

CASE PRESENTATION: 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.

CONCLUSION: 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.

View larger version (242K): [in this window] [in a new window]   Posteroanterior(top) and lateral(bottom) CXR’s demonstrating an approximately 2-cm RUL nodule.

View larger version (193K): [in this window] [in a new window]   Chest-CT characterizing RUL lesion, mediastinal(top) and lung(bottom) windows.

View larger version (306K): [in this window] [in a new window]   Low(top) and high(bottom) power magnification of the RUL specimen.

REFERENCES

1. Hasleton P.S, Spencer’s Pathology of the Lung. 5th Edition 1996McGraw-Hill, New York
2. Zaidi et al. PB: Medium-term Results from a Regional Center. Annuals of Thoracic Surgery. 2002;73:1572–1575
3. Zavala-Alarcon et al. Extension of a PB into the Left Atrium. Mayo Clinic Proceedings. 2001;76:657–660
4. Chin et al. PB in an Adult Presenting as a Chronic Loculated Effusion: a diagnostic problem. Thorax. 1994;49:838–839
5. Vassilopoulos et al. PB Presenting with Massive Hemothorax. Chest. 1992;102:649–650
6. Ghaffer et al. PB: A Report of Two Cases. Chest. 1975;67:600–602
7. Gould et al. Accuracy of PET for Diagnosis of Pulmonary Nodules and Mass Lesions. JAMA. 2001;285(7):914–924