Percentage of cold nodules that becomes malignant are
**Core Concept**
Cold nodules are thyroid nodules that are hypoechoic and have a low vascularity on ultrasound. They are often associated with a low risk of malignancy. However, the risk of malignancy in cold nodules is not negligible and can vary depending on several factors.
**Why the Correct Answer is Right**
The risk of malignancy in cold nodules is estimated to be around 5-10%. This is because cold nodules can be benign thyroid adenomas or cysts, but they can also be malignant thyroid tumors such as papillary, follicular, or anaplastic thyroid cancer. The risk of malignancy is higher in nodules larger than 1 cm, nodules with irregular margins or microcalcifications, and nodules with a history of radiation exposure. Fine-needle aspiration biopsy (FNAB) is often used to determine the malignant potential of cold nodules.
**Why Each Wrong Option is Incorrect**
**Option A:** 0.5% - This is too low, as even benign nodules have a small risk of malignancy.
**Option B:** 20% - This is too high, as most cold nodules are benign.
**Option C:** 1% - This is too low, as the risk of malignancy in cold nodules is generally higher than this.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the risk of malignancy in cold nodules increases with age, with the majority of malignant nodules being diagnosed in patients over 60 years old. A thorough clinical evaluation and imaging studies should be performed to assess the malignant potential of cold nodules.
**Correct Answer: D. 5-10%**