Mesenchymal Hamartoma in an Adult

2014-10-08 07:56:50

Category: Abdominal Imaging, Region: Abdomen-Liver, Plane: Other

Clinical Summary A 27 year old woman with no significant past medical history presented with increasing right upper quadrant and right upper shoulder discomfort. Physical exam demonstrated a nontender enlarged liver. Laboratory values including serum transaminases were unremarkable. Tumor markers such as alpha-fetoprotein, carcinoembryonic antigen, human chorionic gonadotropin, and carbohydrate antigen19-9 were negative. Imaging Findings Abdominal computed tomography (CT) and magnetic resonance imaging (MRI) studies demonstrated a large, complex cystic and solid lesion arising in the caudate lobe of the liver with major vascular involvement (Fig. 1). Contrast enhanced CT of the abdomen demonstrated that the caudate lobe of the liver was near completely replaced by the mass, which contained low attenuating no enhancing multiloculated cystic portions and enhancing solid stroma and septations (Fig. 1A-C). The main portal vein was anteriorly displaced by the tumor, the inferior vena cava was posteriorly displaced by the tumor, and the hepatic veins were seen traversing the displaced/compressed liver. The gallbladder was compressed and anteriorly displaced and contained gallstones. MRI of the abdomen again showed the caudate lobe of the liver to be near completely replaced by the mass with multiloculated nonenhancing cystic portions that were hypointense on T1-weighted images and hyperintense on T2-weighted images with progressively enhancing solid stroma and septations (Fig. 2A-F). No restricted diffusion was seen in the mass. Clinical Course/Operative Summary Given the location of the mass in the caudate lobe, ex-vivo resection with auto-transplantation of the liver was deemed the safest approach for resection by the surgeon. Initially intraoperative biopsies of the caudate lobe mass were performed and found to be nondiagnostic on frozen sections. Cold perfusion of the liver with ex-vivo caudate lobe resection containing the entirety of mass followed by hepatic auto-transplantation was then performed. A massive pseudoencapsulated solid and cystic lesion extending from the caudate lobe was seen intraoperatively, displacing the porta hepatis anteriorly and rotating the right kidney inferiorly and anteriorly (Fig. 3A). The porta hepatis was splayed open and the portal vein bifurcation was pushed anteriorly by the mass, which extended inferiorly to the level of the celiac axis. No normal liver was seen between the hepatic veins and this lesion. The hepatic veins were draped over the mass, which compressed both the IVC and hepatic veins. The hepatic artery was stretched across the lesion. The liver itself appeared normal with the exception of the caudate lesion. The IVC and hepatic veins were resected and reconstructed with additional reconstruction of the hepatic artery and portal vein as part of the autotransplantation of the liver. A choledocholedochostomy was also performed. The patient tolerated the procedure well and had a relatively uneventful post-surgical hospital course. She subsequently recovered well, and an MRI performed 5 months after resection demonstrated no evidence of residual or recurrent disease. Pathologic Evaluation Gross surgical specimen of the caudate lobe showed a white-tan to tan-brown encapsulated mass measuring 13.5 x 9.5 x 5.5 cm and weighing 290 g (Fig. 3B). The specimen was serially sectioned revealing red-brown soft tissue admixed with white opaque mucoid areas with numerous septations, some thick and fibrous. In addition, there was a small portion of tan-brown soft tissue beneath the capsule measuring 4.0 x 1.0 x 0.5 cm. No definite liver parenchyma was identified. Microscopic sections showed a low grade, paucicellular tumor with both fibrous and myxoid areas (Fig. 4). Frequent small, benign-appearing bile ducts were seen at the periphery, with some extending for a short distance into the tumor. A few areas with features suggestive of smooth muscle differentiation were seen. There was an abrupt, well-demarcated transition between the tumor and the surrounding hepatic parenchyma. Areas of extensive intratumoral hemorrhage were present. No areas with high-grade cytologic features were seen. Overall, the findings were most consistent with mesenchymal hamartoma. FIGURE 1. Delayed-phase postcontrast axial (A), coronal (B), and sagittal (C) CT images demonstrate that the caudate lobe of the liver is near completely replaced by a mass consisting of low-attenuating nonenhancing multiloculated cystic portions as well as enhancing solid stroma and septations. The portal vein is anteriorly displaced by the tumor and the inferior vena cava is posteriorly displaced by the tumor. Hepatic veins are seen in the displaced/compressed liver. The compressed gallbladder is anteriorly displaced and contains gallstones. FIGURE 2. Noncontrast axial fat-saturated (A) and coronal non-fat-saturated (B) T2-weighted MR images demonstrate the caudate lobe of the liver to be near completely replaced by a mass containing multiloculated cystic portions, solid stroma and septations. The cystic portions are hyperintense and the solid portions and septations are hypointense or isointense to the normal liver parenchyma on T2-weighted images. Precontrast axial T1-weighted fat-saturated MR image of the caudate lobe (C) shows that the cystic portions are hypointense and the solid portions and septations are mildly hypointense or isointense to the normal liver parenchyma. Delayed postcontrast axial (D), coronal (E), and sagittal (F) T1-weighted fat-saturated MR images of the caudate lobe show the nonenhancing cystic portions and progressively enhancing solid portions and septations. The portal vein is anteriorly displaced by the tumor and the inferior vena cava is posteriorly displaced by the tumor. Hepatic veins are seen in the displaced/compressed liver. The anteriorly displaced and compressed gallbladder is seen containing gallstones. FIGURE 3. Intraoperative gross image of the intact caudate lobe mass (A) demonstrates ex vivo resection of the caudate lobe lesion from normal liver. Photograph of the resected caudate lobe containing the mass in gross cut section (B) demonstrates multiple cystic areas with numerous septations and solid stromal/mesenchymal regions. FIGURE 4. Photomicrograph at 4X magnification of the sectioned caudate lobe of the liver (hematoxylin-eosin stain) (A) demonstrates the well-circumscribed mesenchymal hamartoma with an abrupt, well-demarcated transition between the tumor and the surrounding normal hepatic parenchyma. A low grade, paucicellular tumor with both fibrous and myxoid areas is noted. At the top right, a small benign appearing bile duct extends into the tumor. Photomicrograph at 10X magnification of the sectioned caudate lobe of the liver (hematoxylin-eosin stain) (B) demonstrates the edge of the well-marginated mesenchymal hamartoma with a rim of normal liver parenchyma. Abrupt, well-demarcated transition between the tumor and the surrounding hepatic parenchyma is seen. Benign appearing bile ducts are seen along the edge of the tumor. Photomicrograph at 10X magnification of the sectioned caudate lobe of the liver (hematoxylin-eosin stain) (C) demonstrates the interior of the mesenchymal hamartoma, which was composed of a fibromyxoid stroma of bland spindle cells and thick collagen bundles