Hurthle Cell Carcinoma
Hurthle Cell Carcinoma (HCC)
Hurthle cell carcinoma (HCC) of the thyroid was considered to be s a variant of follicular thyroid carcinoma (FTC) in the past, but because the outcome is slightly worse, it was classified as a separate entity. It makes less than 5% to 7% of all thyroid tumors. So-called Hurthle cells are cells that have undergone oncocytic change (cellular change characterized by an abundant eosinophilic granular cytoplasm).
Hurthle cell carcinoma is spread by blood but also can spread to neck lymph nodes. It has been shown that up to 34% of HCC tumor cells have extrathyroidal spread, up to 56% lymph nodes metastases, and up to 50% distant metastases. Hurthle cell carcinoma can be multifocal in 33% of patients. Mortality rate could be as high as 40%.
Ultrasound-guided fine needle aspiration (FNA) biopsy is the first step in evaluation of any thyroid nodules and establishing the initial diagnosis of malignancy or suspicious for malignancy (follicular or Hurthle cell neoplasm). Preoperative diagnosis by FNA biopsy is very difficult and surgery may be needed for ultimate diagnosis. Fifteen to thirty percent of FNA biopsies that have findings of a "Hurthle cell neoplasm" will have final diagnosis of Hurthle Cell Carcinoma after the surgery.
Many surgeons consider a total thyroidectomy as an appropriate therapy for Hurthle cell carcinoma. A total thyroidectomy with ipsilateral central neck lymphadenectomy and a modified radical neck dissection, if central or lateral nodes are positive, has also been suggested for Hurthle cell carcinoma. The completeness of this procedure should be assessed by radioiodine scan 3 to 4 months after surgery.
Hurthle cell carcinoma poorly takes up radioactive iodine-131. Fewer than 10% of these cancers take up radioiodine. Nevertheless, since it is produces thyroglobulin, the treatment with radioactive iodine still prolongs the time without disease progression and improves survival. Any thyroid remnant should be ablated with radiolabeled iodine 131 to eliminate all tissue at risk and to facilitate the use of serum thyroglobulin in surveillance for tumor recurrence. Recurrent disease is treated surgically with good palliation and appreciable prolongation of life. Local excision and neck dissection for recurrent neck disease or pulmonary wedge resection for lung metastasis has been shown to be effective. All patients with Hurthle cell carcinoma should be given thyroid hormone because most of these tumors have thyrotropin receptors. External beam radiation may be considered for patients with unresectable disease, but this is considered palliative.
Tumor size more than 4 cm, extent of vascular invasion, presence of mitosis, a solid or trabecular growth pattern, extrathyroidal extension and presence of lymph node metastases are among the histologic features that predict recurrence. Extensive vascular invasion was also found to strongly correlate with worse 5-year disease-free interval and disease-specific survival. Hurthle cell carcinoma exhibits a higher rate of distant metastases than papillary and follicular carcinomas. This tumor produces thyroglobulin which can also be used as a marker to monitor treatment response. Five--year survival rates for Hurthle cell carcinoma have been reported to be between 45% to 96%, and ten-year survival rates have been reported to be between 45% and 80%.
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