The Radiologic and Pathologic Diagnosis of Biphasic Pulmonary Blastoma

Abstract

Pulmonary blastomas are rare malignancies, representing 0.25% to 0.5% of all primary lung neoplasms with often aggressive progression and poor prognosis. Clinical management of pulmonary blastomas depends on histologic subtype, staging, and presentation, and may consist of surgery, chemotherapy, and radiation. Biphasic pulmonary blastoma is a subtype of pulmonary blastoma that exhibits biphasic histology, with both epithelial and mesenchymal malignant elements. We report a case of biphasic pulmonary blastoma in a 33-year-old female with 1 pack per day history of smoking for approximately 16 years, who presented with left-sided pleuritic chest pain on deep inspiration without otherwise significant pat medical history. Imaging evaluation using chest radiography, computed tomography, and magnetic resonance imaging identified a heterogenous, well-circumscribed, left lower lobe mass with extensive necrosis and hemorrhage. No lymphadenopathy or distant metastasis was detected through imaging evaluation. Surgical resection of the tumor followed by histopathological analysis confirmed a biphasic pulmonary blastoma.

Keywords: Biphasic Pulmonary Blastoma; Computed Tomography; Magnetic Resonance Imaging; Pulmonary Blastoma; Pulmonary Neoplasm.

Figure 1

A 33-year-old female with biphasic pulmonary blastoma. Technique: Chest radiograph with anteroposterior view (A) and lateral view (B) Findings: There is a large, round, and well-circumscribed lesion projecting over the left lower lung zone on the frontal projection, which localizes to the lower lobe on the lateral projection (arrows). The left cardiac silhouette remains distinct. There is no evidence of hilar lymphadenopathy, erosive changes in the adjacent ribs, or presence of a pleural effusion.

Figure 2

A 33-year-old female with biphasic pulmonary blastoma. Technique: Contrast-enhanced CT of the chest. Axial images at the level of the lower lung zone, with mediastinal window (A, level: 30, window: 300) and mediastinal/lung window (B, level: -300, window: 2000). Coronal (C) and sagittal (D) images with mediastinal/lung window (level: -300, window: 2000). Findings: There is a 7 cm, solitary, low density, well-circumscribed, minimally heterogenous mass noted in the left lower lobe (asterisk). Subadjacent atelectasis of the lung is seen without infiltrative changes. Posteriorly, the mass abuts the pleural surface. There is no bony changes or clear evidence of chest wall invasion. No lymphadenopathy or additional pulmonary lesion is identified. Splaying of the left lower lobe segmental bronchi is seen. The mass does not contact the more central hilar or mediastinal structures.

Figure 3

A 33-year-old female with biphasic pulmonary blastoma. Technique: Contrast-enhanced CT of the abdomen and pelvis with mediastinal window (level: 30, window: 300). Axial images at the level of the cardiac atria (A) and ventricles (B) as well as coronal (C) and sagittal (D) images through the mass. Findings: On the abdominal images, there is partially seen and now better appreciated central heterogenous irregular areas of internal contrast enhancement within the lesion (asterisk), consistent with viable soft tissue component. The thick and mildly irregular peripheral component is now seen. The central soft tissue component measures 40 HU while the nonenhancing component measures 18 HU. Areas of atelectasis are again noted.

Figure 4

A 33-year-old female with biphasic pulmonary blastoma. Technique: MRI axial view of the chest with fast spin echo T1 (A) and T2 (B) weighted images with coronal T2 (C) and coronal SSFP (D) images. Findings: (A) The left lower lobe mass is noted to contain relative T1-hypointense areas of septations internally with otherwise relative T1-hyperintense central region, corresponding to the hypodense region on prior CT and consistent with increased protein content or hemorrhage. The soft tissue component of the mass (peripheral ring and internal septations) appear T1 hyperintense when compared to skeletal muscle. (B) On T2 images, the internal septations are better appreciated on the background of T2-hyperintense central region. A trace amount of pleural fluid is noted posteriorly. The heterogenous and complex nature of the lesion is also noted on the coronal images (C and D).

Figure 5

A 33-year-old female with biphasic pulmonary blastoma. Technique: MR T1 weighted images of the chest with fat suppression prior to (A) and following (B) contrast administration in axial view as well as post-contrast images in sagittal (C) and coronal (D) views. Findings: The left lower lobe mass appears well-circumscribed without infiltrative changes. The peripheral thick irregular rim and central areas of hair-like, curvilinear septations demonstrate avid enhancement: compare precontrast (A) and postcontrast (B) axial images.

Figure 6

A 33-year-old female with biphasic pulmonary blastoma. Technique: Ventilation-perfusion scan using 133Xe INH and 99mTc macroaggregated albumin IV. Findings: Nuclear ventilation-perfusion scan of the lungs for pre-operative lung function evaluation demonstrates large photopenic defect in the left lower lobe on both ventilation (A) and perfusion (B), corresponding to the known lesion. The split function was estimated at approximatley 40–60 left to right split.

Figure 7

A 33-year-old female with biphasic pulmonary blastoma. Technique: Portable AP radiographs of the chest (A and B) with normal PA frontal (C) and lateral (D) radiographs of the chest. Findings: Pre-operative frontal radiograph of the patient demonstrates the known large left lower lobe mass (A). Portable frontal radiograph of the chest after left lower lobectomy demonstrates expected postsurgical changes with two chest tubes in place on the left (B). The lesion is no longer seen. Follow-up radiographs 1 year after surgery demonstrate changes of prior left lower lobectomy without evidence of recurrence (C and D).

Figure 8

A 33-year-old female with biphasic pulmonary blastoma. Technique: Gross surgical specimen of the resected tumor. Findings: The opened gross specimen demonstrates a well-circumscribed tumor, measuring approximately 7 cm. The peripheral aspect of the mass is solid. Internally, areas of soft tissue as well as hemorrhage (arrows) are seen.

Figure 9

A 33-year-old female with biphasic pulmonary blastoma. Technique: Low power field (A, original magnification × 100) and high power field (B and C, original magnification × 400) microscopic images with hematoxylin and eosin stains from the tumor Findings: (A), (B), and (C) shows the tumor to be biphasic with malignant, but primitive, glandular and stromal elements.