Hurthle Cell Carcinoma
Definition
Hurthle Cell Carcinoma is a type of tumor of the thyroid gland.
Description
A Hurthle cell tumor is a growth of the thyroid gland composed wholly or predominantly of large cells (Hurthle cells). Such tumors are usually benign (Hurthle cell adenoma) but on occasion may be locally invasive or, rarely, may metastasize (Hurthle cell carcinoma or malignant Hurthle cell tumor). This term was first used in 1928 by Ewing who described these tumors as being composed of cells identical to a particular interfollicular cell which had been described by Hurthle in 1894 in normal canine (dog) thyroid glands. Some physicians consider Hurthle cell carcinoma as an additional category of well-differentiated thyroid carcinoma rather than a subcategory of follicular carcinoma.
Causes
There is a clear-cut female to male predominance ranging from 2:1 to 10:1 among patients with Hurthle cell neoplasms. The peak incidence is in the fifth and sixth decades. Patients with Hurthle cell carcinomas tend to be older, with peak ages of incidence in the seventh and eighth decades, whereas papillary and, to a lesser extent, follicular carcinomas of the thyroid gland occur in younger patients. Hurthle cell neoplasms of the thyroid gland have a variable and unpredictable course. The malignant potential of some Hurthle cell neoplasms is well documented by their ability to recur locally, metastasize to lung and bone, and cause death. Consequently, it is accepted that clearly identified Hurthle cell carcinomas are potentially life-threatening and should be managed with an aggressive surgical approach. However, considerable dispute exists regarding the clinicopathologic criteria used to determine which lesions require aggressive surgical management and which require conservative treatment. The presence of even a large collection or nodule of Hurthle cells in a thyroid gland does not necessarily imply a neoplastic lesion. Hurthle cells are associated with other non-neoplastic, inflammatory conditions such as thyroiditis, Graves' disease, and nodular lesions of the thyroid. Approximately 30 percent of patients with Hurthle cell carcinomas are found to have previous, coexisting, or subsequent non-malignant thyroid disease. The presence of multiple nodules composed of Hurthle cells without encapsulation and found in association with another nodular lesion of the thyroid gland represents a non-neoplastic, inflammatory, or reactive process. Hurthle cell neoplasms comprise approximately 4.5 percent to 10 percent of all primarily epithelial tumors. On the other hand, the reported incidence of Hurthle cell carcinoma is 0.4 percent to 10 percent of all thyroid carcinomas. The distinction between benign and malignant Hurthle cell neoplasms and the correlation between their histopathologic characteristics and the biological behavior of these lesions remains the central and most critical issue regarding the management of the neoplasms.
Treatment
The treatment is controversial because of the unreliable correlation between histopathologic features and clinical behavior. It appears that Hurthle cell neoplasms exhibit a biologic behavior similar to that of corresponding follicular cancers, although these latter tumors may have a higher tendency to metastasize. Some surgeons have reported that Hurthle cell neoplasms are usually benign lesions and are not likely to demonstrate a clinically malignant course. Others have reported that Hurthle cell neoplasms are of only moderate malignant potential. Others still have reported that the biological behavior of Hurthle cell neoplasms can be accurately predicted by the histopathologic characteristics of the lesion. However, there are those who have reported that all Hurthle cell neoplasms should be considered potentially malignant and, therefore, should be treated aggressively because histopathologic criteria cannot always differentiate benign from malignant tumors. Survival and cure rates are lower than those for papillary cancer and are comparable to those for follicular cancer.
Questions
What tests need to be performed to diagnose the condition and the cause? Is there a coexisting thyroid disease? What types of cells are involved in the tumor? What is the potential for malignancy? Will thyroidectomy be recommended?
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