Follicular thyroid cancer arises from the hormone-producing follicular cells of the thyroid gland and is the second most common type of thyroid cancer after papillary cancer. It usually presents as a single nodule and, unlike the papillary type, tends to spread through the bloodstream rather than to the lymph nodes. When diagnosed at an early stage, its course is usually favourable.
What is follicular thyroid cancer?
Under the microscope its cells form small sacs (follicles) resembling normal thyroid tissue. It is more common in regions where iodine deficiency is widespread and in middle to older age. The defining feature of this type is whether the tumour cells have breached the capsule surrounding the nodule or its blood vessels; the diagnosis of cancer is based on this capsular and vascular invasion. Tumours that breach the capsule only to a limited extent are classified as “minimally invasive”, while those showing clear spread into blood vessels or surrounding tissue are classified as “widely invasive”. Hürthle cell (oncocytic) cancer, formerly regarded as a subtype of follicular cancer, is a separate type that is managed in a similar way.
Symptoms
- A slow-growing, painless, single nodule at the front of the neck
- With large nodules, a feeling of pressure in the throat and difficulty swallowing
- Rarely, hoarseness
- When distant spread has occurred, bone pain or lung complaints may be the first finding; this is uncommon
Diagnosis
Ultrasound and fine-needle aspiration biopsy are the first steps. However, a definitive diagnosis of follicular cancer by biopsy is difficult: the cells of a benign follicular adenoma and of follicular cancer look alike, and the difference becomes clear only when the whole nodule is removed and its capsule and vessels are examined under the microscope for invasion. For this reason, when the biopsy result is reported as “follicular neoplasm” or “indeterminate”, removal of the affected lobe is recommended for diagnostic purposes. In some centres, molecular tests on the biopsy sample can also help in decision-making.
Treatment
If the pathology after a diagnostic lobectomy shows a benign lesion or minimally invasive cancer, no further surgery is usually needed. When widely invasive cancer is found, removal of the rest of the gland (completion thyroidectomy) followed by radioactive iodine treatment is planned; radioactive iodine is particularly important in this type because of its tendency to spread through the bloodstream. As lymph node involvement is less common than in the papillary type, neck dissection is performed only when involvement is found. When the whole gland is removed, thyroid hormone medication is started. If there is distant spread, radioactive iodine and, when needed, radiotherapy and targeted drugs are used.
After surgery and follow-up
Follow-up is carried out with neck ultrasound and the thyroglobulin level in the blood. Because of the possibility of distant spread, a whole-body iodine scan or other imaging is added when necessary. Follow-up continues for many years.
When should you see a doctor?
If you have a growing nodule in your neck, a feeling of pressure in the throat or complaints such as unexplained bone pain, it is advisable to see a doctor. If your biopsy result has been reported as “indeterminate” or “follicular neoplasm”, it is important to discuss the next step with your doctor.
Frequently asked questions
Why can a biopsy not confirm follicular cancer?
The cells of a benign follicular adenoma and of follicular cancer look alike; the difference becomes clear only when the removed nodule's capsule and blood vessels are examined under the microscope.
Does follicular cancer spread to the lymph nodes?
Less often than the papillary type. This type tends to spread through the bloodstream, for example to bone or lung, and follow-up is planned accordingly.
Is a second operation needed after lobectomy?
Usually not if the pathology shows minimally invasive cancer. In widely invasive cancer, the rest of the gland is removed and radioactive iodine treatment is planned.
This page is general information. Decisions about diagnosis and treatment are made for you personally, and only after an examination. If you have symptoms, see a doctor.