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Background: Hepatoid tumors (HTs) are rare extra-hepatic neoplasms with the histological features, biochemical profile and, sometimes, even clinical course of hepatocellular carcinoma. We present a case of rectal hepatoid adenocarcinoma with metachronous liver metastases., Methods: Four months after total procto-colectomy for a rectal adenocarcinoma (Astler-Coller C2), a 42-year-old man with ulcerative colitis showed hypoechoic masses in the hepatic parenchyma by abdominal ultrasonography. Carcinoembryonic antigen was normal, but alpha-fetoprotein was 32,000 microg/L. Fine-needle biopsy revealed that liver masses were positive for hepatocellular carcinoma. The patient underwent left hepatectomy and alcoholisation of a small deep nodule in segment 8., Results: Immunohistochemistry and albumin mRNA in situ hybridization suggested that the nodules were metastases of a HT. The patient was well during the first 6 months and refused any adjuvant chemotherapy. He died from liver failure 19 months after initial diagnosis., Conclusions: HT is a rare colon cancer. The preoperative diagnosis of this tumor requires a high degree of suspicion, the availability of a panel of immunohistochemical markers, and a certain amount of luck. The prognosis is poor despite an aggressive and multimodal therapeutic strategy. So far, none of the hypotheses proposed about the origin and the biology of these tumors is convincing.

Five chemicals that are known to induce in rats thyroid follicular-cell adenomas and carcinomas were assayed for their ability to induce DNA damage and DNA repair synthesis in primary cultures of human thyroid cells. Significant dose-dependent increases in the frequency of DNA single-strand breaks and alkali-labile sites, as measured by the same Comet assay, were obtained after a 20-h exposure to the following subtoxic concentrations of the five test compounds: methimazole from 2.5 to 10mM; nitrobenzene, potassium bromate, N,N'-diethylthiourea and ethylenethiourea from 1.25 to 5mM. Under the same experimental conditions, DNA repair synthesis, as evaluated by quantitative autoradiography, was present in potassium bromate-exposed thyroid cells from all the three donors and in those from two of three donors with either nitrobenzene or ethylenethiourea, but did not match the criteria for a positive response in thyroid cells from any of the donors with methimazole and N,N'-diethylthiourea. Consistently with their ability to induce thyroid tumors, all the five test compounds, administered p.o. in rats in a single dose corresponding to 1/2 LD50, induced a statistically significant degree of DNA fragmentation in the thyroid. These findings suggest that the five test compounds might be carcinogenic to thyroid in humans.