In the present case, we reported a case of a patient with liver metastasis of PTC presenting with elevated serum levels of CA19-9 after total thyroidectomy. The major sites of distant metastases from PTC are the lung and bone. However, to date, there have been few reports of liver metastases in patients with PTC [1,2,3,4,5,6,7]. As liver metastases are usually found along with other distant metastases sites and are nearly always multiple or diffuse , it is even more unusual to encounter isolated resectable liver metastases from PTC. In the present case, the patient also had metastases in the lung, cervical spine and mediastinum.
Tg is a very sensitive and specific marker in patients who have undergone total thyroidectomy for PTC; disease progression correlates with increasing serum levels of Tg in PTC patients. However, the presence of TgAb interferes with Tg immunometric assays, making the Tg levels unreliable indicators [8, 9]. The prevalence of TgAb in PTC patients is reported to be 25%, higher than that (10%) in the normal population [8, 9], and follow-up by Tg levels is not appropriate for these patients. Therefore, currently, there are no useful tumor markers to follow up on in patients who are serum TgAb-positive.
CA19-9 was originally isolated from a colorectal cancer cell line as a mucin-like product. This antigen is found in the normal epithelial cells of the gall bladder, biliary ducts, pancreas and stomach; therefore, CA19-9 is typically considered a gastrointestinal tumor marker. However, in one report, CA19-9 was observed in the tissues of ~ 6% of the patients with medullary thyroid carcinoma (MTC) . Furthermore, Elisei et al.  and After examining 100 patients with advanced MTC, Lorusso et al.  reported that an elevated value of serum CA19-9 appears to be a predictive factor of poor prognosis in advanced MTC patients and could identify cases with a higher risk of mortality in the short term. Similarly, Alencar et al.  reported that serum CA19-9 might have a role as a prognostic factor in MTC patients. In addition, there are also a few reports on the relationship between PTC and CA19-9 [14,15,16,17,18,19,20]. Hashimoto et al.  and Vierbuchen et al.  found that the positive immunohistochemical staining rates for CA19-9 in PTC tissues were 58% and 48%, respectively. In one case report, serum CA19-9 showed low sensitivity as a tumor marker in a patient with thyroid carcinoma ; in another case report, the serum level of serum CA19-9 was elevated at the time of the growth and/or recurrence of PTC and proved a useful tumor marker . Yamaguchi et al.  found that the serum level of CA19-9 was elevated before excision of the lung metastasis of PTC and decreased to within normal limits thereafter. In the present case, the histopathological diagnosis of the liver lesion was metastasis from PTC, and the immunostaining was positive for both CA19-9 and Tg. In addition, the primary PTC tissue resected 16 years ago was immunohistochemically stained and found to be positive for CA19-9. Furthermore, the high serum levels of both CA19-9 and Tg decreased considerably after resection of liver metastasis.
The serum levels of CA19-9 in previously reported patients with liver metastasis of PTC were normal in one patient and not described in 4 patients [3,4,5,6,7]. Since serum levels of CA19-9 are not usually measured in patients with PTC, the percentage of elevated serum CA19-9 levels in patients with PTC is not known. To our knowledge, high serum levels of CA19-9 in patients with liver metastasis of PTC have not been previously reported. The present report is the first reported case of a patient with liver metastasis of PTC presenting with elevated levels of serum CA19-9. If the patients with PTC have positive serum TgAb, it may be useful to immunostain the lesions for CA19-9 as a tumor marker, as in the present case. Especially, it may be a potential alternative tumor marker to Tg in PTC patients with positive serum TgAb. We recommend immunostaining the lesions for CA19-9 as a surrogate marker when the serum TgAb is positive in patients with PTC. However, of course, if the immunostaining of CA19-9 is negative in the primary thyroid lesions and metastases, the serum level of CA19-9 will not be an appropriate tumor marker.