What is Hurthle Cell Thyroid Carcinoma?
Generally, thyroid cancers have been categorized into four types: papillary, follicular, medullary, and anaplastic. These types (papillary, follicular, and medullary) are grouped under differentiated thyroid tumors, meaning they look a lot like normal thyroid tissue. Hurthle cell carcinoma (HCC), a less commonly known thyroid cancer type, used to be considered a form of follicular thyroid cancer as it shared certain similarities, such as how it appears and its metastatic spread – which means how the cancer spreads to other parts of the body. However, in 2017, the World Health Organization decided to classify it as a distinct type of tumor due to its substantial differences with follicular thyroid cancer in both cell structure and molecular makeup. So now, Hurthle cell thyroid cancer is defined as a cancer that originates from follicular thyroid cells, rather than being a variant of follicular cancer itself.
What Causes Hurthle Cell Thyroid Carcinoma?
There’s no direct cause known yet for Hurthle cell thyroid cancer. However, certain things can increase your chances of getting it. For example, if you have been exposed to radiation in the areas of your head, neck, or chest, or if your family has a history of thyroid cancer, you may be more likely to get thyroid cancers.
Risk Factors and Frequency for Hurthle Cell Thyroid Carcinoma
Hurthle cell carcinoma, a type of thyroid cancer, makes up about 5% of all differentiated thyroid cancers. It’s more common in women and is usually diagnosed after the age of 40.
Signs and Symptoms of Hurthle Cell Thyroid Carcinoma
Hurthle cell cancers, a type of thyroid cancer, are usually discovered when patients have thyroid nodules, or when these nodules are spotted unexpectedly during neck scans. In more advanced stages, the cancer may present itself as swollen glands in the neck, known as ‘cervical adenopathy’. In rare cases, the first sign of this disease could be cancer spreading to distant parts of the body, also known as ‘distant metastasis’.
Testing for Hurthle Cell Thyroid Carcinoma
If a health professional identifies suspicious growths or lumps (nodules) in your thyroid gland, they will typically recommend a few tests to check its functionality. These tests include thyroid-stimulating hormone (TSH) and thyroxine (T4) levels. The existence and size of the nodules can be further confirmed through an ultrasound scan.
If your TSH level is low, this could indicate a functional nodule. In this case, a radioiodine imaging scan is typically used to confirm. Functionally hyperthyroid, or “hot”, nodules are rarely cancerous, but they may require treatment to manage an overactive thyroid (hyperthyroidism) or excessive thyroid hormone in the body (thyrotoxicosis).
If the nodules don’t make excessive thyroid hormone (non-thyrotoxic thyroid nodules), a fine-needle aspiration (FNA) and biopsy might be recommended. FNA involves inserting a thin needle into the nodule to collect a sample of cells. This technique can accurately diagnose some types of thyroid cancer, like papillary and anaplastic thyroid cancers.
However, when it comes to follicular and Hurthle cell tumor types, FNA might be insufficient to determine if it’s benign (non-cancerous) or malignant (cancerous). Usually, a larger portion of the thyroid needs to be removed (thyroid lobectomy or thyroidectomy), after which a detailed examination of the removed tissue will be conducted to identify invasive cancer.
In recent times, molecular studies have gained prominence to differentiate between benign and malignant tumors derived from follicular cells. This has helped in avoiding unnecessary aggressive surgeries. These tests include looking for BRAF and RAS mutations, mRNA genomic sequencing, and checking the expression of certain genes through microRNA gene expression modalities.
In some cases, if widespread disease is suspected based on your symptoms, your doctor may recommend other imaging tests like computed tomography (CT) or magnetic resonance imaging (MRI). Laryngoscopic evaluation could be necessary if you are experiencing issues with your voice (dysphonia) or difficulty swallowing (dysphagia).
In patients suspected of having the disease spread to other parts of the body (metastatic disease), a special type of imaging that combines PET and CT scans (PET-CT) might be useful.
Treatment Options for Hurthle Cell Thyroid Carcinoma
Surgery is the primary treatment for a type of cancer called Hurthle cell tumors. Two types of surgery, thyroid lobectomy (partial removal of the thyroid) and total thyroidectomy (complete removal of the thyroid), have been found to have similar results for non-invasive Hurthle cell tumors. If the cancer is invasive, however, a total thyroidectomy is needed.
Radioactive iodine (RAI) is often used as a secondary treatment for cases where the cancer is harder to treat, such as having a larger tumor, spread to the neck lymph nodes, cancerous cells at the edge of the surgically removed tissue, invasion into small blood vessels, or high levels of a protein called thyroglobulin after surgery. However, only around 10% of Hurthle cell carcinoma patients respond to this treatment, making it less effective than for other types of thyroid cancers. This is because most Hurthle cell carcinomas don’t absorb iodine, so a negative RAI scan may not necessarily mean there’s no cancer left. For these high-risk patients, an FDG-PET scan is recommended, which can help detect cancer cells more accurately.
If the cancer is present in the neck (cervical disease) after initial treatment, neck dissection (a surgery to remove lymph nodes) can be considered. If surgery is not possible or advisable, then radiation therapy may be an option.
For patients who have Hurthle cell carcinoma that has spread to other parts of the body (metastatic), the choice of treatment depends on several factors. If the patients have no symptoms and the tumor is growing slowly, it may be possible to just monitor the condition. If the tumor is growing rapidly and absorbs iodine, RAI is preferred. On the other hand, if the tumor does not respond to RAI, certain medications like lenvatinib or sorafenib may be used. However, these medications can have side effects, and lenvatinib is typically preferred over sorafenib.
There’s also data supporting the use of drugs like larotrectinib or entrectinib for tumors with specific genetic changes, and pembrolizumab for tumors with a high number of mutations. Similarly, selpercatinib and pralsetinib may be beneficial for patients with RET fusion, a specific genetic change that can occur in cancers. If no other treatments work, chemotherapy may be used as a last resort, although it hasn’t been shown to help significantly in Hurthle cell carcinoma cases.
What else can Hurthle Cell Thyroid Carcinoma be?
Hurthle cell carcinoma is a type of thyroid cancer that shares a lot of similarities with other forms of thyroid cancers, especially follicular thyroid carcinoma. However, there are some key differences.
- Hurthle cell carcinomas are often bigger in size than follicular thyroid carcinomas.
- They tend to have more than one tumor (multifocal).
- There is a higher chance of Hurthle cell carcinomas spreading to other parts of the thyroid (local thyroid invasion), to the lymph nodes (lymph node metastases), and to distant parts of the body (distant metastases).
- They have unique features when studied under a microscope (histological features), and unlike other types, they show low uptake of radioactive iodine in medical imaging.
Fast-growing thyroid carcinomas should always be checked for anaplastic thyroid carcinoma. This type is more dangerous and needs immediate treatment. This treatment could include chemotherapy and radiation therapy for the neck.
What to expect with Hurthle Cell Thyroid Carcinoma
Hurthle cell carcinomas are types of cancers that are believed to be more severe and spread more easily compared to follicular thyroid carcinomas, which are another type of thyroid cancer. This results in lower overall survival rates according to certain medical reviews.
Factors that contribute to a worse prognosis, or outcome, for Hurthle cell carcinomas include older age, a larger tumor size when first diagnosed, the tumor spreading beyond the thyroid, being female, and having a higher stage, or severity, at the time of diagnosis.
Possible Complications When Diagnosed with Hurthle Cell Thyroid Carcinoma
The complications associated with Hurthle cell carcinomas are similar to those seen in general thyroid growths. These complications occur when the carcinoma starts spreading to nearby areas in the neck such as the voice box, vocal cords, esophagus, windpipe, or area between the lungs, and by putting pressure on critical nerves and blood vessels due to swollen lymph nodes. The cancer might also spread, or metastasize, to the lungs, bones, and occasionally, the brain.
Complications of Hurthle cell carcinomas:
- Spread to nearby throat structures (voice box, vocal cords, esophagus, windpipe, or area between the lungs).
- Pressure on crucial nerves and vessels in the neck from swollen lymph nodes.
- Spreading of cancer to lymph nodes, lungs, and bones.
- Less commonly, spreading to the brain.
Preventing Hurthle Cell Thyroid Carcinoma
Hurthle cell carcinomas, a type of thyroid cancer, can be more aggressive than other types of thyroid cancers. Currently, there are no standard methods to screen for thyroid tumors recommended for use in people who don’t show any symptoms, according to the United States Preventive Services Task Force. However, individuals with a family history of a specific type of thyroid cancer known as medullary thyroid carcinomas, multiple endocrine neoplasias (a grouping of disorders that affect the body’s endocrine system), a personal history of thyroid cancer, familial adenomatous polyposis syndrome (an inherited condition that causes precancerous polyps to grow in the colon), or those who have been exposed to radiation, are at a high risk of developing thyroid cancer. These high-risk individuals should be made aware of any suspicious signs and symptoms and should remain vigilant. Moreover, they need to understand the importance of getting any unusual thyroid nodules (small lumps of cells) or neck masses checked out promptly.
