British Journal of Radiology (2005) 78, 437-440
© 2005 British Institute of Radiology
doi: 10.1259/bjr/45172814
Pulmonary blastoma: presentation of two atypical cases and review of the literature
R I Walker, MRCP1,
K Suvarna, MRCP FRCPath2 and
S Matthews, MRCP, FRCR1
Departments of 1 Radiology and 2 Pathology, Northern General Hospital, Herries Road, Sheffield S5 7AU, UK
Correspondence: Dr S Matthews, Consultant Radiologist
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Abstract
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Pulmonary blastoma is a relatively rare aggressive adult malignancy. The clinical and radiographic features of two cases are described and the literature reviewed. Pulmonary blastoma usually presents radiologically as a well-defined mass lesion on chest radiography, which may be large enough to completely opacify the hemithorax and cause mediastinal shift. On CT, pulmonary blastoma is seen as a mixed solid and cystic lesion with variable contrast enhancement and a necrotic centre. Pleural effusion may be present but is not the predominant abnormality. Our cases are unusual as recurrent pleural effusions in the absence of a significant lung mass were the presenting findings.
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Introduction
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Pulmonary blastomas are a relatively rare group of primary lung neoplasms that are composed of immature malignant epithelial and/or mesenchymal tissues whose features may resemble early embryological lung tissues [1]. First described by Barnard in 1952, they have been divided into three subgroups – classic pulmonary blastoma (PB), well-differentiated fetal adenocarcinoma (WDFA) and pleuropulmonary blastoma (PPB) of childhood [1, 2]. The radiological appearance of PB is typically described as a well-circumscribed mass lesion [3, 4]. We present two cases of classic biphasic pulmonary blastoma (CBPB) which presented with pleural disease as the main abnormality.
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Case reports
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Case 1
A 21-year-old white Caucasian woman presented with a 3 week history of shortness of breath, non-productive cough, fever and right-sided non-pleuritic chest pain. She had received two courses of oral antibiotics without improvement in her symptoms. She was a non-smoker, who was previously fit and well. Signs of a right pleural effusion led to a clinical diagnosis of empyema. Initial investigations showed a neutrophil leucocytosis (19 x 109 l–1), thrombocytosis (745 x 109 l–1), reduced serum albumin (26 g l–1) and mild liver impairment (AST 71 IU l–1). On the chest radiograph there was complete opacification of the right hemithorax with contralateral mediastinal shift consistent with a large pleural effusion (Figure 1
). A litre of blood stained pleural fluid was removed at pleurocentesis. Cytopathological examination of the pleural fluid revealed a poorly cellular specimen with mixed inflammatory cells, mesothelial cells and no evidence of malignancy. Bacterial cultures of the pleural fluid were negative. A contrast enhanced CT of the thorax confirmed a large right pleural effusion with associated mediastinal shift and almost complete collapse of the right lung. In addition, multiple ring enhancing cystic structures were identified in the pleural space. There was extensive mediastinal lymphadenopathy predominantly involving the right paratracheal, precarinal and subcarinal locations (Figure 2). No abnormality was seen in the left hemithorax or upper abdomen.
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Figure 1. Case 1: Chest radiograph at presentation shows complete opacification of the right hemithorax with contralateral mediastinal shift.
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Figure 2. Case 1: Enhanced CT of the thorax showing a large right pleural effusion with contralateral mediastinal shift, mediastinal lymphadenopathy and multiple ring enhancing cystic structures within the pleural cavity.
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The patient was transferred to the regional cardiothoracic surgical centre for further management. Complete drainage of the pleural effusion was unsuccessfully attempted via an intercostal drain. Hence, she underwent a right thoracotomy and decortication. At surgery the pleura was extensively thickened. The pleural cavity revealed large masses of debris with adherent deposits on the diaphragm. The right middle lobe was obliterated. Large pericardial lymph nodes were found and sampled.
The pathology examination revealed fragments of thickened pleural tissue with sheets of pleomorphic immature cells. Scattered mitoses were present together with widespread areas of irregular necrosis. Immunohistochemistry revealed positive pan-cytokeratin staining in addition to reactivity for BerEp4, CK7 and EMA. Negative reactions were seen with thyroglobulin, CA125, PLAP, CD45, CD56, CEA, vimentin, CD34, CD31 and CD99. The overall appearances were consistent with a PB (Figure 3).
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Figure 3. Case 1: Histological specimen showing highly pleomorphic polygonal cells with pronounced nuclear atypia. (Haematoxylin and eosin stain, magnification x 400).
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Her post-operative course was complicated by a deep vein thrombosis in the right internal jugular vein. A subsequent CT scan revealed significant residual tumour medially within the right upper hemithorax and extensive mediastinal lymphadenopathy, features of superior vena cava obstruction (requiring stent insertion) and lymphangitis in the right upper lobe. She commenced chemotherapy but her disease progressed with the development of bone metastases. She died less than 6 months after initial presentation.
Case 2
A 41-year-old white Caucasian woman presented with a 2 month history of shortness of breath and chest pain. She was a smoker (five per day) but had no significant past medical or therapeutic history. Clinical examination was unremarkable. Investigations revealed a normocytic normochromic anaemia (Hb 7.9 g dl–1), neutrophil leucocytosis (25 x 109 l–1), thrombocytosis (658 x 109 l–1), reduced serum albumin (30 g l–1) and raised inflammatory markers (ESR 105, CRP 113). The chest radiograph showed a small left pleural effusion that was confirmed on ultrasound (Figure 4a). At diagnostic aspiration, the pleural fluid was heavily blood stained. No evidence of malignancy was detected at cytopathological examination. Culture of the pleural fluid was negative.
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Figure 4. Case 2: Serial chest radiographs demonstrating (a) the presenting chest radiograph and (b) enlargement of the left pleural effusion 1 month later.
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1 month after the initial presentation, the patient developed progressive shortness of breath owing to enlargement of the pleural effusion (Figure 4b
) and complained of tingling and paraesthesia in her arms. A CT head scan showed two enhancing mass lesions in her right frontal lobe consistent with cerebral metastases. A CT of the thorax demonstrated a large left pleural effusion with contralateral shift of the mediastinum (Figures 5a,b). There was extensive diffuse pleural thickening involving the mediastinal pleural and multiple enhancing cystic structures within the pleural space. There was mild enlargement of the subcarinal lymph nodes. At bronchoscopy, there was complete obstruction to the left lower lobe bronchus but no endobronchial lesion was identified. The patient was transferred to the regional cardiothoracic surgical centre and underwent left thoracotomy and mediastinoscopy. At thoracotomy, a large quantity of organized blood clot and a partially necrotic left lower lobe was found. The haematoma was evacuated and a partial left lower lobectomy was performed.
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Figure 5. Case 2: Contrast enhanced CT of the thorax showing (a) a left pleural effusion with mediastinal shift and diffuse mediastinal pleural thickening and (b) multiple enhancing pleural cysts with peripheral pleural thickening.
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Histology revealed irregular haemorrhagic and partly necrotic beige tissue fragments containing a high grade epithelioid neoplasm with polygonal cells showing a high nuclear: cytoplasmic ratio. Immunohistochemistry revealed positive cytokeratin, EMA and vimentin reactivity. No staining was seen with cytokeratin 5/6, calretinin, AFP, CD34, CD31, S100 protein, HMB45, PLAP, BerEp4, CA19.9, CA125, alpha-actin, desmin and AUA1. The findings were consistent with a high grade PB.
Cranial palliative radiotherapy was given. Post-operative imaging showed increasing infiltration of her lung. She was treated symptomatically, and died 4 months after the initial presentation.
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Discussion
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PB is a rare tumour accounting for 0.25–0.5% of malignant lung neoplasms [1, 5]. Originally termed "embryoma" by Barnard in 1952 [2], the term blastoma was introduced in 1961 by Spencer to reflect that the tumours arise from the pulmonary blastema in a similar manner to other tumours developing from fetal tissue [6]. Subsequently PB have been further subdivided by Koss et al [1] into three categories: CBPB, WDFA and PPB. CBPB is the most common of these three subtypes.
WDFA usually affects middle-aged adults, often with a tobacco smoking history, and has a pathogenesis similar to that of bronchogenic carcinoma. Prognosis is usually better than bronchogenic carcinoma. PPB are rare intrathoracic tumours, occurring predominantly in children less than 3 years old. Approximately 80% of CBPB occurs in adults [1]. However, two peaks in age are described in the first and fourth decades and cases have been reported from 0 to 80 years [5]. There is a slight male predominance. In adults there is an association with cigarette smoking and in children CBPB has been seen in association with pre-existing benign cysts of the lung [3, 5, 7]. A p53 gene mutation with or without p53 protein overproduction has been linked to both CBPB and WDFA [8]. Yousem et al consider that CBPB develop from a pluripotent blastema that gives rise to the epithelial and mesenchymal tumour components [9]. This view is supported by the observed simultaneous expression of cytokeratin and vimentin in the blastomatous component. These pluripotent cells may be stimulated through genetic and/or environmental influences to differentiate.
In general CBPB presents with non-specific respiratory symptoms that may mimic a respiratory tract infection: cough, haemoptysis, dyspnoea and chest pain [8]. 40% of cases are asymptomatic and found coincidentally on chest radiographs performed for other indications. The chest radiographic appearance usually consists of a well-circumscribed mass measuring 1.5 cm to 13 cm in diameter [1, 3, 4]. In children the lesion often completely fills the affected hemithorax to produce contralateral mediastinal shift [3]. In adults the lesion usually presents as a solitary peripheral nodule [3]. The tumour appears to be located either peripherally or centrally and there is no definite lobar predominance. In children pre-existing lung disease may be noted. CBPB may rarely present as a spontaneous pneumothorax [10, 11]. There has been a single case of PB presenting as a chronic lobulated pleural effusion that was initially diagnosed as pleural tuberculosis [12]. On ultrasound CBPB presents as an echogenic or mixed echogenic mass that may contain cystic areas [13]. This is comparable with the CT appearance of a partly solid/partly cystic lesion with a necrotic centre [8, 11]. The mass may have a whorled appearance and display variable contrast enhancement. The presence of pleural or mediastinal involvement is an indication of metastatic disease.
PB is an aggressive tumour associated with a poor prognosis. Surgery is the preferred treatment, often with post-operative adjuvant chemotherapy and/or radiotherapy [3]. Prognosis is worse if the tumour is larger than 5 cm at presentation. Distant metastases are frequently seen.
Our cases are unusual as in both cases pleural effusion was the predominant abnormality and a pulmonary mass lesion was not evident. In Case 1 empyema was the original working diagnosis. Ultrasound or CT of the chest ultimately revealed a more complex problem, with a multicystic enhancing intrapleural mass. The diagnosis ultimately required histology. In both cases the presentation and radiology were more in keeping with pleuropulmonary blastoma, a tumour of childhood. There have been several reported cases of PPB simulating chronic empyema [14, 15]. The CT scan in PPB has been reported to show multilocular cystic lesions in the pleural space similar to our cases [16]. These similarities may reflect the common origin from the pulmonary blastema.
These cases highlight the importance of excluding a malignant cause for a pleural effusion, even in young adults, and that PB should be considered in the differential diagnosis.
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Acknowledgments
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We would like to acknowledge the contributions of Mr R Vaughan and Mr D Hopkinson; the thoracic surgeons involved in managing the patients' care.
Received for publication August 13, 2004.
Revision received November 12, 2004.
Accepted for publication January 5, 2005.
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References
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Abstract
Introduction
