PMC5362868_01
Thoracic ultrasonography demonstrating the lesion in cross-section: the mass has a heterogeneous echogenicity and is surrounded by hypoechoic free fluid caudal to the heart
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Transthoracic ultrasonography identified a 4.27 cm heterogeneous mass (measured in a medial to lateral plane) caudal to the heart (Figure 1).
CT angiography of the thorax, sagittal reconstruction: the mass is present within the pericardial sac and caudal to the contrast-enhancing heart. The mass has a mild and heterogeneous pattern of contrast enhancement and is in continuity caudally with the mesenteric fat
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The CT scan demonstrated that the intrathoracic mass was continuous with the intra-abdominal lobes of the liver and extended cranially through a large diaphragmatic defect into the pericardial space (Figure 2).
Image of the mass dissected away from the heart during exploratory thoracotomy
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A 5 x 6 x 7 cm firm, irregular, tan-coloured soft tissue mass was visualised surrounding the heart on the right side and within the pericardial cavity (Figure 3).
Histopathology of the lesion - malignant, markedly pleomorphic spindle cell proliferation invading small islands of hepatic tissue (H) (haematoxylin and eosin, x 40)
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Histological examination of the mass revealed a malignant, markedly pleomorphic spindle cell proliferation that invaded and compressed small regions of hepatic parenchyma embedded within the mass (Figure 4).
Marked collagenous matrix production by the mass (M) staining pink, adjacent to and invading a small island of hepatocytes (H) (Van Gieson's, x 100)
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Some of the cells formed a collagenous matrix (confirmed with Van Gieson's staining) (Figure 5); however, the majority showed no differentiation.
Invasion of malignant spindle cells within sinusoids causing attenuation and atrophy of hepatocytes. The isolated islands of hepatic tissue within the mass had essentially normal hepatic architecture, although there was invasion of the sinusoids by the malignancy (haematoxylin and eosin, x 200)
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Immunohistochemical staining with vimentin antibody shows strong positive staining of malignant mass cells (M) and negative staining of hepatocytes (H) (vimentin, x 100)
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Immunohistochemical staining was performed to determine the origin of the tumour using antivimentin antibody (stains mesenchymal, mesothelial and round cells [hepatocytes stain negative]) (Figure 7).
Immunohistochemical staining with cytokeratin AE1/AE3 antibody shows negative staining of malignant mass cells, negative staining of hepatocytes and strong positive staining of occasional remnant biliary structures (arrow) (cytokeratin AE1/AE3, x 200)
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The proliferating cells in the mass were negative for AE1/AE3, although multifocal sparsely distributed bile ducts within the mass stained strongly positive (Figure 8).