Spontaneous
hepatocellular carcinoma has been reported as a relatively common
neoplasm in prosimians; however, the cause is unknown. To investigate possible pathogenic mechanisms, the authors performed a review of all adult animals from a captive prosimian population that had postmortem examinations over the past 10 years. They performed a detailed histologic evaluation of all suspected proliferative liver lesions and diagnosed
hepatocellular carcinoma in 14 of 145 lemurs (9.7%). Affected animals ranged between the ages of 6 and 40 years old. The
tumors had an unusually aggressive growth pattern for animal species;
metastasis to the lungs or mediastinum was evident in 7 of 14 animals. Thirty-one animals-9 with
hepatocellular carcinomas and 22 age-matched controls without hepatic
neoplasia-were tested to evaluate the relationship between hepatic
iron stores (as well as other trace metals) and the presence of
hepatocellular carcinoma. There was no difference between the hepatic
iron,
copper, or
molybdenum in lemurs with
hepatocellular carcinoma and those without, suggesting that
iron is not a key
element in the pathogenesis of liver
tumor formation. Analysis of 22 serum samples from animals with and without liver
tumors indicated no evidence of active
infection with a hepadnavirus, the virus family that includes hepatitis B virus. Hepatitis C virus and
aflatoxin B1 were considered as potential causes and ruled out owing to lack of associated histopathologic lesions. In conclusion, hepatocellular
neoplasia is relatively common in captive prosimians, although previously suspected etiologies seem unlikely.