Hepatic adenoma

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An hepatocellular adenoma, cut along its long axis, demonstrating the thermally ablated necrotic areas within the tumour[1]

Hepatocellular adenomas are a benign neoplasm of the canine liver characterized by a large diffuse multilobulated liver mass[2].

These tumors are usually slow-growing masses which are commonly diagnosed as an incidental finding on ultrasonography or at postortem and rarely cause clinical disease.

Hepatic adenoma are characterized by a characteristic well-circumscribed and demarcated growth similar to nodular hyperplasia and can grow quite large[3]. They are usually single, may be quite large (up to 20 cm) and often exhibit a pedunculated attachment.

These tumours occur with a higher frequency than the malignant counterpart, and usually occur in dogs over 10 years of age.

Adenomas consist of a friable, highly vascular parenchyma, and rupture with subsequent haemoperitoneum may be the clinical presentation[4].

These tumors rarely causes physical symptoms until the interfere with normal hepatic function and may then cause abdominal distension, ascites, lethargy, anorexia and weight loss.

Diagnosis is usually achieved with radiographic or ultrasonographic imaging. With ultrasonography, these tumors may exhibit malignant contrast-enhanced characteristics and results should be interpreted cautiously. A fine-needle biopsy should be interpreted histologically for evidence of adenocarcinomatous changes[5].

Histologically, these tumours may be difficult to distinguish from nodular hyperplasia or even normal liver tissue. Histologically, encapsulation and compression of adjacent hepatic parenchyma are characteristic features. Immunohistochemical staining with cytokeratin and hepatocyte paraffin 1 may help achieve a definitive diagnosis[6].

A differential diagnosis includes biliary cystadenoma[7], hepatic carcinoma, hepatic lymphoma, hepatitis, nodular hyperplasia, vacuolar change, fibrosis, metastatic neoplasia, necrosis, hepatic lipidosis, round cell tumour, steroid hepatopathy, extramedullary haematopoiesis and secondary metastases (e.g. hemangiosarcoma)[8].

Complete surgical resection is curative but by the time of diagnosis high tumour burden may make this unachievable. Chemotherapy may be the only option in the treatment of unresectable hepatocellular adenoma, using doxorubicin[9].

The prognosis for respectable hepatocellular adenomas is good, and survival times of up to 2 years have been reported[10].

References

  1. Kopelman D et al (2006) Magnetic resonance-guided focused ultrasound surgery (MRgFUS). Four ablation treatments of a single canine hepatocellular adenoma. HPB (Oxford) 8(4):292-298
  2. Magne ML & Withrow SJ (1985) Hepatic neoplasia. Vet Clin North Am Small Anim Pract 15(1):243-256
  3. Fukushima K et al (2012) CT characteristics of primary hepatic mass lesions in dogs. Vet Radiol Ultrasound 53(3):252-257
  4. Liptak JM et al (2004) Liver tumors in cats and dogs. Compend Contin Educ Pract Vet 26:50–6
  5. Toaldo MB et al (2012) Imaging diagnosis - cholangiocellular adenoma: Contrast-enhanced ultrasonographic findings of a benign tumor mimicking malignant neoplasia in a dog. Vet Radiol Ultrasound Oct 24
  6. Ramos-Vara JA et al (2001) Immunohistochemical characterization of canine hyperplastic hepatic lesions and hepatocellular and biliary neoplasms with monoclonal antibody hepatocyte paraffin 1 and a monoclonal antibody to cytokeratin 7. Vet Pathol 38(6):636-643
  7. Moon SJ et al (2011) Biliary cystadenoma in a Maltese dog: clinical and diagnostic findings. J Vet Med Sci 73(12):1677-1679
  8. Warren-Smith CM et al (2012) Lack of associations between ultrasonographic appearance of parenchymal lesions of the canine liver and histological diagnosis. J Small Anim Pract 53(3):168-173
  9. Cave TA et al (2003) Treatment of unresectable hepatocellular adenoma in dogs with transarterial iodized oil and chemotherapy with and without an embolic agent: a report of two cases. Vet Comp Oncol 1(4):191-199
  10. Hammer AS & Sikkema DA. Hepatic neoplasia in the dog and cat. Vet Clin North Am Small Anim Pract 25:419–35
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