From the Guidelines
Yes, angioinvasive carcinoma of the thyroid is considered a form of differentiated thyroid cancer, specifically a subtype of follicular carcinoma. According to the World Health Organization (WHO) classification, follicular carcinoma is characterized by capsular invasion and vascular invasion, with angioinvasive carcinoma referring to the presence of neoplastic emboli involving more than 4 blood vessels 1. This classification is supported by the European Society for Medical Oncology (ESMO) clinical practice guidelines for diagnosis, treatment, and follow-up of thyroid cancer, which notes that follicular carcinomas can be minimally invasive or widely invasive, with angioinvasive carcinoma being a subtype of the latter 1.
Key Characteristics of Angioinvasive Carcinoma
- Angioinvasive carcinoma is a subtype of follicular carcinoma
- Characterized by vascular invasion with neoplastic emboli involving more than 4 blood vessels
- Classified as a differentiated thyroid cancer, which typically maintains many of the biological and morphological features of normal thyroid tissue
- Generally has a better prognosis compared to poorly differentiated or undifferentiated thyroid carcinomas
Clinical Implications
- The presence of vascular invasion is an important prognostic factor that physicians consider when determining treatment plans
- Treatment approaches may include more extensive surgery, radioactive iodine therapy at higher doses, and closer surveillance
- Understanding the distinction between angioinvasive carcinoma and other types of thyroid cancer is crucial for proper management and prognostication of thyroid cancer 1.
Molecular Profiling
- Molecular profiling has distinguished two major classes of papillary thyroid carcinomas (PTCs) characterized by BRAF-predominant and RAS-predominant molecular signatures
- BRAF V600E mutations are frequently reported in a subgroup of PTCs with more aggressive clinicopathological behaviors
- The molecular profiles of follicular and Hu¨rthle cell carcinomas are less well-defined, with ongoing work to define the genomic and transcriptomic profiles of poorly differentiated and anaplastic thyroid carcinomas 1.
From the Research
Definition of Differentiated Thyroid Cancer
- Differentiated thyroid cancer (DTC) includes papillary, follicular, and Hürthle cell carcinoma, which account for more than 90% of new thyroid cancer diagnoses 2.
- DTC is characterized by its excellent prognosis, with current treatment including surgery, radioactive iodine ablation, and postoperative thyroid-stimulating hormone suppression 2.
Angioinvasive Carcinoma of the Thyroid
- Angioinvasive carcinoma of the thyroid refers to the invasion of thyroid cancer into blood vessels, which is a poor prognostic factor for patients with DTC 3.
- Angioinvasion is often seen in aggressive forms of follicular cell-derived thyroid cancer, such as poorly differentiated thyroid cancer and anaplastic thyroid cancer 4.
- However, angioinvasion can also occur in well-differentiated thyroid cancer, including papillary thyroid cancer, which is the most common type of thyroid cancer 5.
Classification of Angioinvasive Carcinoma
- Angioinvasive carcinoma of the thyroid can be considered a form of differentiated thyroid cancer, as it arises from thyroid follicular cells and retains some degree of differentiation 4.
- However, the presence of angioinvasion is a indicator of aggressive disease, and patients with angioinvasive carcinoma may require more aggressive treatment, including surgery, radioactive iodine, and targeted therapies 3, 4.
- The classification of angioinvasive carcinoma as a form of DTC is supported by studies that have shown that angioinvasion is an independent predictor of distant metastasis at presentation in patients with papillary thyroid cancer 5.