Follicular thyroid carcinoma
Follicular thyroid carcinoma is the second most common differentiated thyroid cancer, accounting for 10% to 15% of thyroid cancer cases, and characteristically spreads hematogenously to lung, bone, and brain rather than to cervical lymph nodes. Because fine-needle aspiration cytology cannot reliably distinguish it from a benign follicular adenoma, diagnosis often requires diagnostic lobectomy, and treatment is surgery followed by postoperative radioactive iodine and thyroid-stimulating-hormone-suppressive levothyroxine for higher-risk disease.
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What this article covers
- Overview
The second most common differentiated thyroid cancer: follicular thyroid carcinoma (FTC) accounts for 10% to 15% of thyroid cancer cases, arising from thyroid hormone-producing follicular cells, the…
- Epidemiology
Accounts for 10% to 15% of thyroid cancer diagnoses, making it substantially less common than papillary thyroid carcinoma, which accounts for the majority of cases.
- Risk factors
RAS mutations: a recognized molecular driver associated with follicular thyroid carcinoma.
- Pathophysiology
Malignant transformation of thyroid follicular cells: like papillary thyroid carcinoma, follicular thyroid carcinoma arises from thyroid hormone-producing follicular cells, distinguishing it from…
- Clinical features
A thyroid mass or nodule: the usual presentation, similar to papillary thyroid carcinoma, though without the cervical lymphadenopathy that is common in PTC.
- Differential diagnosis
Follicular adenoma: the key benign mimic; distinguished from follicular carcinoma only by the absence of capsular and vascular invasion on histology, since fine-needle aspiration cytology cannot reliably tell the two apart.
- Diagnosis
The diagnosis is established histologically by demonstrating invasion of the tumor capsule and vasculature in a follicular-patterned thyroid lesion, since fine-needle aspiration cytology alone often…
- Management
First, perform surgery, the mainstay of treatment: diagnostic lobectomy for a follicular-patterned nodule of uncertain cytology, followed by completion thyroidectomy if carcinoma with invasion is…
- Complications
Distant metastases to lung, bone, or brain: the characteristic and most consequential pattern of spread in follicular thyroid carcinoma, reflecting its hematogenous route.
- Prognosis
Generally good, though influenced by the extent of invasion and presence of distant metastases: follicular thyroid carcinoma is described as having a good prognosis overall, though hematogenous…
- Prevention
No specific primary prevention exists for sporadic follicular thyroid carcinoma, since it arises from acquired molecular alterations (RAS mutations, PAX8-PPAR-gamma translocations) rather than a modifiable exposure in most patients.
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Related articles
- Papillary thyroid carcinoma
Papillary thyroid carcinoma is the most common thyroid malignancy, arising from thyroid follicular cells and typically spreading to cervical lymph nodes with a low risk of distant metastasis. Diagnosis rests on ultrasound risk stratification and fine-needle aspiration biopsy, and treatment is thyroid lobectomy or total thyroidectomy, with postoperative radioactive iodine and thyroid-stimulating-hormone-suppressive levothyroxine reserved for intermediate to high risk disease.
- Medullary thyroid carcinoma
Medullary thyroid carcinoma is a neuroendocrine tumor of the parafollicular C cells that secretes calcitonin and is familial (RET-mutant, part of MEN2A or MEN2B) in about 25% of cases. First-line treatment is total thyroidectomy with central neck lymph node dissection, with any coexisting pheochromocytoma resected first, followed by lifelong levothyroxine replacement and calcitonin/CEA surveillance; selpercatinib, a RET kinase inhibitor, is used for unresectable or metastatic RET-mutant disease.
- Anaplastic thyroid carcinoma
Anaplastic thyroid carcinoma is a rare, highly aggressive, undifferentiated thyroid malignancy that presents as a rapidly enlarging neck mass, arising de novo or from a preexisting differentiated thyroid cancer, and is often unresectable at diagnosis with a median survival of about 5 months. Treatment is largely palliative multimodality therapy with surgery when feasible, external beam radiation therapy, and chemotherapy, since the disease has typically outpaced the possibility of cure by the time it is recognized.
- Thyroid nodules
A thyroid nodule is a discrete structural lesion within an otherwise normal thyroid gland, found on ultrasound in about 40% of the United States population though palpable in far fewer, and malignant in roughly 5%. Evaluation begins with a thyroid-stimulating hormone (TSH) level and thyroid ultrasonography, and management is surveillance for benign or low-risk nodules, with lobectomy or total thyroidectomy reserved for cytology suspicious for or diagnostic of malignancy.