Single liver metastasis of a follicular variant of papillary thyroid carcinoma: a rare pattern of organ spread.

SUMMARY: Well-differentiated thyroid cancer (WDTC), including papillary, follicular, and Hurthle-cell types, is characterized by a slow course and usually remain localized to the thyroid. However, a minority of these cases develop distant metastases with the most common sites being lungs, bones, and lymph nodes. Liver metastases of WDTC are rare and are usually found along with other distant metastases sites and in a multiple or diffuse pattern of spread. The recognition of distant metastasis in WDTC has a significant impact on the treatment and prognosis. However, because of their low incidence and awareness, distant metastases are often diagnosed late. Herein, we describe a case of a 71 years old woman who during routine surveillance of a follicular variant of papillary thyroid cancer (FV-PTC), 5 years after being treated for her primary thyroid tumor, was found to have a single liver metastasis and underwent liver segmental resection. This case highlights the importance of maintaining vigilant surveillance of patients with WDTC, and illustrates the possibility of unique metastasis at unexpected sites. Further studies are needed to understand the organ tropism of some WDTC leading to distant metastases development and to better prediction of an aggressive course. LEARNING POINTS: WDTC patients with distant metastases have a poor prognosis with a 10-year survival of about 50%. The most common sites of distant metastases are lung, bone and lymph nodes. Liver metastases are rare in WDTC, are usually multiple or diffuse and are found along with other distant metastases sites. Single liver metastasis of WDTC is an unexpected pattern of spread, and very few cases are reported in the literature. Rare sites of distant metastases in WDTC can manifest many years after the primary tumor, stressing the importance of maintaining vigilant surveillance. More studies are needed to predict which WDTC tumors may develop a more aggressive course, allowing clinicians to individualize patient management.