Hurthle cell thyroid carcinoma is a type of cancer arising from follicular cells, one of the cells in the thyroid tissue. The reason is not known exactly. A history of radiation exposure to the head and neck region, which is at risk for thyroid cancer, family history and the transformation of existing thyroid diseases can be counted among the causes.
Huthle cell carcinoma is a family of differentiated carcinomas of the thyroid. It accounts for about 5% of cancers of this family. It is more common in women over 40 years of age.
Benign Hurthle cell adenomas can also be seen as malignant carcinomas that protrude beyond their capsule and show increased blood supply. Malignant forms have the feature of metastasizing to surrounding lymph nodes and distant tissues. Hurthle cell carcinomas tend to be larger than other follicular thyroid carcinomas.
The appearance of Hurthle cells, eosinophilic oxyphilic cells with round to oval nuclei with prominent nucleoli, in Hurthle cell carcinoma tissue is characteristic for diagnosis. These Hurthle cells are also known as oncocytes or Askanazy cells. Hurthle cells can also be seen in non-malignant thyroid diseases. If more than 75% of Hurthle cells are seen in the examined tissue, they are classified as Hurthle cell malignancies.
Hurthle cell carcinomas are detected incidentally during examination of thyroid nodules. In advanced cases, enlargement of the lymph nodes in the neck can also be seen.
Diagnosis of Hurthle cell thyroid carcinoma:
Routine thyroid hormone profile is examined in patients with suspected thyroid disease. Thyroid nodule is evaluated with thyroid ultrasonography or other imaging methods. At the same time, it is examined whether the lymph nodes in the neck are affected.
Even if the thyroid hormones are normal or high during the thyroid hormone profile, low TSH indicates an increase in the functions of the thyroid gland. Cancer can rarely be detected in these active thyroid glands. Concomitant hyperthyroidism or thyrotoxicosis may also be seen.
In cases where a thyroid nodule is detected, non-overactive thyroid nodules can be examined with fine needle aspiration biopsy. Fine-needle aspiration biopsy alone is not sufficient to make a diagnosis. Definitive diagnosis is made by tissue examination after thyroidectomy. Because increased blood supply in the tissue, follicle integrity or capsule damage showing invasion to surrounding tissues may not be seen in aspiration biopsy.
Computed tomography or magnetic resonance imaging can be performed in patients with symptoms of pressure on surrounding tissues. PET-CT can be applied in cases where tissue metastasis is thought.
Treatment of Hurthle cell thyroid carcinoma:
The treatment of Hurthle cell thyroid carcinoma is surgery. Total thyroidectomy is usually preferred. Thyroid replacement therapy may be required for life, as hypothyroidism may develop after thyroidectomy. Risks and complications from the surgery itself can also develop. Complications related to surgery can usually be controlled. The process may take a little longer if the patient has another disease that prevents or slows wound healing.
Radioactive iodine therapy is less effective in Hurthle cell thyroid carcinoma than in other thyroid cancers. However, it is widely used in cases of high-risk features such as tumor size greater than 2 cm, cervical lymph node metastases, positive margins, microvascular invasion, or postoperative thyroglobulin levels greater than 1 ng/mL.
In metastatic Hurthle cell carcinomas, observation is an acceptable option for asymptomatic patients as long as they do not have brain metastases. However, radioactive iodine therapy is a preferred option for metastatic patients with symptoms or rapidly growing tumors.
In patients who are not suitable for radioactive iodine therapy, tyrosine kinase inhibitors such as lenvatinib or sorafenib can be used for systemic chemotherapy. Levatinib has a more acceptable side-effect profile. In addition, agents such as pembrolizumab, selpercatinib and pralsetinib can also be used. Cytotoxic chemotherapy is less effective and can be applied as a last option.
Rapidly growing thyroid carcinomas should always be examined for anaplastic thyroid carcinomas. Because anaplastic thyroid carcinomas are much more aggressive and have a worse prognosis.
Hurthle cell thyroid carcinomas show more aggressiveness and less survival than follicular thyroid carcinomas. Advanced age, larger tumor size at diagnosis, extrathyroidal spread, female gender, and higher grade at diagnosis are considered poor prognostic features in these patients.