Encapsulated angioinvasive follicular carcinoma is a specific type of thyroid cancer, originating from the cells that produce thyroid hormones. It represents a well-differentiated carcinoma, meaning the cancer cells generally resemble normal thyroid cells when viewed under a microscope. This form of thyroid cancer requires careful evaluation and management.
Understanding Encapsulated Angioinvasive Follicular Carcinoma
The term “encapsulated angioinvasive follicular carcinoma” describes specific features of this thyroid cancer.
“Encapsulated” indicates that the tumor is enclosed within a clear, fibrous outer layer or capsule. This capsule helps define the tumor’s boundaries.
“Follicular” refers to the origin of the cancer cells, which are the follicular cells of the thyroid gland. These cells produce thyroid hormones. Under a microscope, these cancer cells appear arranged in small, round structures similar to normal thyroid follicles.
“Angioinvasive” means cancer cells have invaded blood vessels either within or just outside the fibrous capsule. This invasion into blood vessels is a defining characteristic that differentiates it from other less aggressive follicular thyroid tumors. Angioinvasion raises the risk of cancer cells spreading through the bloodstream to other parts of the body, such as the lungs or bones.
“Carcinoma” is a general term for a type of cancer that begins in the lining or covering of an organ. In this context, it signifies a malignant tumor originating from the epithelial cells of the thyroid gland.
Identifying This Thyroid Cancer
The diagnostic process for encapsulated angioinvasive follicular carcinoma begins with the detection of a thyroid nodule. This nodule might be discovered during a routine physical examination or incidentally found during imaging tests performed for other reasons. A lump or swelling in the neck is a common initial finding, though some individuals may experience no symptoms at all.
Thyroid ultrasound is a common imaging tool used to assess the nodule’s size, composition, and vascularity. Blood tests, such as those measuring thyroid-stimulating hormone (TSH) levels, are also conducted to evaluate thyroid function.
Fine Needle Aspiration (FNA) biopsy involves taking a cell sample from the nodule for microscopic examination. While FNA can suggest the presence of a follicular neoplasm, it cannot definitively distinguish between a benign follicular adenoma and a malignant follicular carcinoma, including the angioinvasive type. This limitation is due to the need to identify capsular or vascular invasion, which cannot be reliably assessed through an FNA biopsy alone.
A definitive diagnosis of encapsulated angioinvasive follicular carcinoma requires surgical removal of the thyroid nodule or a portion of the thyroid gland. Following surgery, a pathologist conducts a thorough examination of the removed tissue under a microscope. This detailed pathological review is necessary to identify the presence and extent of angioinvasion, confirming the diagnosis.
Treatment Options
Surgical removal of the thyroid gland is the primary treatment for encapsulated angioinvasive follicular carcinoma. The extent of surgery can vary, ranging from a lobectomy, which removes the affected lobe of the thyroid, to a total thyroidectomy, which involves removing the entire thyroid gland. The decision on the extent of surgery depends on factors such as tumor size, location, and the confirmed presence and degree of angioinvasion.
Radioactive iodine (RAI) therapy is administered as an additional treatment after surgery, particularly when angioinvasion is present. This therapy takes advantage of the thyroid gland’s natural ability to absorb iodine. Patients swallow a capsule containing radioactively charged iodine (I-131), which is then absorbed by any remaining thyroid tissue or microscopic cancer cells throughout the body, targeting and destroying them.
Following a total thyroidectomy, lifelong thyroid hormone replacement therapy with levothyroxine is necessary. This medication replaces the hormones normally produced by the thyroid gland, maintaining proper metabolic function. Thyroid hormone replacement also helps suppress the growth of any remaining cancer cells by lowering TSH levels.
Life After Diagnosis and Treatment
The prognosis for encapsulated angioinvasive follicular carcinoma is favorable. However, the presence of angioinvasion necessitates closer long-term monitoring compared to non-invasive forms due to a slightly elevated risk of recurrence or distant spread. The extent of vascular invasion, specifically whether there are fewer than four or two or more foci of invasion, influences this risk. For instance, a 10-year disease-free survival rate of 85.6% has been observed, with better rates for those with limited vascular invasion.
Ongoing surveillance is a regular part of post-treatment care. This includes periodic physical examinations, especially of the neck, to check for any new lumps or swelling. Blood tests are performed to monitor thyroglobulin levels, which act as a tumor marker, and thyroid-stimulating hormone (TSH) levels to ensure appropriate hormone replacement.
Imaging studies, such as neck ultrasounds, are also used to detect any local recurrence. These follow-up visits are scheduled more frequently in the first few years after treatment, such as every 3 to 6 months for the initial two years, and then annually thereafter if there is no evidence of disease. This consistent follow-up, managed by an endocrinologist, helps ensure long-term well-being.