Blastoma

A 16-year-old white boy was admitted to the hospital with a 5-week history of fever, left-sided chest pain, and cough productive of whitish sputum. Physical examination revealed a normally developed teenager with a temperature of 38.8 deg C, a pulse of 110 beats per minute, blood pressure of 110/80 mm Hg, and a respiratory rate of 24 breaths per minute. There were decreased breath sounds and resonance over the left lower chest. Sputum examination revealed no pathogens. A chest radiograph revealed complete opacification of the left lower thorax with a small amount of aerated lung above and a lobulated mass in the right middle lobe (Figure 1). Decubitus films suggested the presence of fluid. A percutaneous needle biopsy of the left lower thorax yielded 250 mL of bloody fluid. The cytologic examination disclosed no neoplastic cells. Computed tomography confirmed a bilateral mass, more prominent in the left hemithorax, showing mediastinal and parietal pleural infiltration. Abnormalities in the results of standard laboratory tests were nonspecific. During a bronchoscopic examination, the patient spontaneously coughed up a thick violaceous tissue fragment (12 x 6 x 4 mm), which was immediately fixed in 10% formalin and submitted for histopathologic examination.

Sections of the fragment showed a glandular proliferation consisting of tubular structures of different sizes separated by spindle stromal elements (Figure 2). The glands were characteristically well developed and consisted of branching tubular structures lined with pseudostratified, nonciliated columnar cells with typically clear cytoplasm caused by glycogen, as shown by reactions with periodic acid-Schiff stain. The cells generally were devoid of pleomorphism and displayed low mitotic activity. No morulae were seen. The epithelial component also showed less-differentiated areas with the cells arranged in sheets, cords, and even rosette-like structures (Figure 3). Glands lined with single cells, which resembled those seen in conventional adenocarcinoma, were occasionally observed. A few keratin pearls were observed as well. The stromal component consisted of a monotonous population of embryonic-appearing oval or spindle cells set against a light myxoid background. Occasionally, the components of the tumor seemed to merge or to coalesce (Figure 3). No anaplastic areas with significant nuclear pleomorphism or heterologous elements were seen. Coagulative necrosis was observed in 40% of the tumor fragment. The diagnosis rendered was biphasic pulmonary blastoma (PB). The patient was considered inoperable owing to mediastinal involvement of the tumor. Chemotherapy with etoposide and cisplatinum was started. He died 1 year after presentation. The diagnosis was confirmed by autopsy.

Pulmonary blastomas are rare primary malignancies of the lung, accounting for 0.25% to 0.5% of primary lung tumors.' They consist primarily of immature epithelial and mesenchymal components and histopathologically resemble the epithelial and stromal components of the fetal lung in the pseudoglandular stage of development. Originally called "pulmonary embryomas" by Barnard,2 Spencer3 later designated these tumors "pulmonary blastomas," suggesting an origin from the pulmonary blastema or a pluripotential mesenchyme. The mean age of patients presenting with PBs is 43 years. Only 20% of tumors occur in individuals younger than 20 years of age., Histologically, the presence of malignant embryonal-like tissues differentiates this neoplasm from others with mixed epithelial and mesenchymal components.4 A strict adherence to the presence of a glycogenated cytoplasm in an endometrioid epithelium confirms the diagnosis of PB.5 Previous studies have emphasized both the generally poor survival rates of patients with PBs and the unpredictability of their clinical course. Based on a survey of published cases, the prognosis of patients with PBs is as poor as that of patients with common lung carcinomas. Although there are individual reports of long-term tumor-free survival, two thirds of patients with PBs die within 2 years of diagnosis.

The histogenesis of PBs is still undetermined. Yousem et al4 observed simultaneous expression of cytokeratin and vimentin in the blastomatous component, which provides some support for the contention that a pluripotential blastema may give rise to the epithelial and mesenchymal elements of PBs. We tentatively suggest that PBs originate from residual embryonic tissue in the lung, which through genetic and/or environmental influences will generate pluripotential cells with different degrees of differentiation. For this reason, a clear distinction between carcinosarcoma and PB is not always possible, so much so that some authors regard PB as a form of carcinosarcoma.6 Since the lung is primarily a foregut derivative, further studies of the antigen profile of the embryonal foregut are needed to better understand the histogenesis of this fascinating tumor.

The authors thank Elaine Medeiros Floriano for her technical assistance, Cleto D. Nogueira, MD, assistant pathologist, and Angela K. C. Bonifacio, MD, resident of pneumology at the University Hospital of Faculty of Medicine of Ribeirao Preto-University of Sao Paulo, for their expert assistance. Simone G. Ramos, MD, PhD, is an investigator of Nacional Council of Scientific and Technological Development, Brazil.

References

1. Koss MN, Hochholzer L, O'Leary T. Pulmonary blastomas. Cancer. 1991; 67:2368-2381.

2. Barnard WG. Embryoma of the lung. Thorax. 1952;7:229-301.

3. Spencer H. Pulmonary blastomas. J Pathol Bacteriol. 1961;82:161-165.

4. Yousem SA, Wick MR, Randhawa P, Manivel JC. Pulmonary blastoma: an immunohistochemical analysis with comparison with fetal lung in its pseudoglandular stage. Am I Clin Pathol. 1990;93:167-175.

5. Colby TV, Koss MN, Travis WD. Tumors of the Lower Respiratory Tract. Rosai J, ed. Washington, DC: Armed Forced Institute of Pathology; 1995:403-406. Atlas of Tumor Pathology, 3rd series, fascicle 13.

6. Addis BJ, Corrin B. Pulmonary blastoma, carcinosarcoma and spindle-cell carcinoma: an immunohistochemical study of keratin intermediate filaments. J Pathol. 1985;147:291-301.

Simone G. Ramos, MD, PhD; Gisele G. Rezende, MD; Adilson A. Faccio, MD

Accepted for publication January 30, 2002.

From the Departments of Pathology (Drs Ramos and Rezende) and Pulmonary Medicine (Dr Faccio), Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil.

Reprints: Simone G. Ramos, MD, PhD, Department of Pathology, Faculty of Medicine of Ribeirao Preto, University of Sao Paulo, Av Bandeirantes 3900, 14049-900 Ribeirao Preto, Sao Paulo, Brazil (e-mail: sgramos@fmrp.usp.br).

Copyright College of American Pathologists Jul 2002
Provided by ProQuest Information and Learning Company. All rights Reserved