Most common histological type of thyroid carcinoma is
**Core Concept**
The most common type of thyroid carcinoma is a well-differentiated tumor that arises from the follicular epithelium of the thyroid gland. Papillary thyroid carcinoma is characterized by its distinctive nuclear features, such as pseudoinclusions and grooves.
**Why the Correct Answer is Right**
Papillary thyroid carcinoma accounts for approximately 80-85% of all thyroid cancer cases. This type of cancer is more common in females and has a relatively good prognosis if diagnosed early. The characteristic nuclear features of papillary thyroid carcinoma, such as pseudoinclusions and grooves, are a result of the abnormal keratinization of the tumor cells. The papillary type of thyroid carcinoma is also known to spread through the lymphatic system, which is why lymph node metastases are common in this type of cancer.
**Why Each Wrong Option is Incorrect**
**Option A:** Follicular type is the second most common type of thyroid carcinoma, but it is less common than papillary type. Follicular carcinoma typically arises from the follicular epithelium of the thyroid gland, but it lacks the characteristic nuclear features of papillary carcinoma.
**Option C:** Anaplastic type is a rare and aggressive form of thyroid carcinoma, accounting for only 1-2% of all thyroid cancer cases. Anaplastic carcinoma is a highly malignant tumor that arises from the undifferentiated cells of the thyroid gland.
**Option D:** Medullary type is a type of thyroid carcinoma that arises from the parafollicular cells (also known as C cells) of the thyroid gland. Medullary carcinoma is less common than papillary type and is often associated with genetic mutations, such as the RET proto-oncogene mutation.
**Clinical Pearl / High-Yield Fact**
Papillary thyroid carcinoma is often associated with radiation exposure, particularly in children and adolescents. Therefore, it is essential to monitor thyroid function and perform regular thyroid ultrasounds in individuals who have received radiation therapy to the head and neck region.
**✓ Correct Answer: B. Papillary type**