Is thyroid cancer the same as a malignant thyroid tumor? In fact, there is a difference between the two. To answer this question, it is important to understand the difference between “cancer” and “malignancy” in medicine.
Difference between “cancer” and “malignant tumor”
There are many types of cells in our body, each with a different form and different functions. All cell types can become malignant and grow into “malignant tumors.
Only malignant tumors derived from epithelial cells are medically known as carcinomas. What are “epithelial cells”? This refers to cells located on the surface of the skin or luminal tract (e.g., digestive tract, respiratory tract).
Malignant thyroid tumors that are not “cancerous”
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In addition to “cancer,” malignant tumors that do not originate from the thyroid epithelium and those that metastasize to the thyroid are also members of the thyroid malignancy family, but are relatively uncommon. The following is a brief overview.
1. Other malignant tumors of the thyroid
The major ones include lymphoma, malignant teratoma, malignant peripheral nerve sheath tumor, angiosarcoma, smooth muscle sarcoma, and follicular dendritic cell sarcoma. All of these tumors are rare. They have the same morphologic features as similar tumors occurring in other organs. Among them, malignant tumors of mesenchymal tissue (e.g., fat, vasculature, bone, cartilage, fibrous tissue, etc.) origin, such as thyroid angiosarcoma, are usually “very malignant.
Relatively common is thyroid lymphoma, which is the only lymphoma that is more prevalent in women. The outcome of limited thyroid lymphoma is better.
2. Secondary malignant neoplasm of the thyroid
This refers to direct spread of malignant tumors from adjacent organs, or dissemination of malignant tumors from distant organs to the thyroid through the bloodstream. They are still tumors of other primary organs. For example, a lung cancer that metastasizes to the thyroid is still a lung cancer and cannot be called a thyroid cancer.
Squamous cell carcinoma of the larynx is the most common of these, and spreads to the thyroid gland through direct invasion. In addition, kidney cancer, lung cancer, breast cancer, colon cancer, melanoma, lymphoma, and nasopharyngeal cancer may also metastasize to the thyroid gland.
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Co-written by Dr. Tingting Zhang, Cancer Hospital of Fudan University