From the Guidelines
No, thyroid cysts are not the same as thyroid nodules, though they are related. Thyroid nodules are abnormal growths of thyroid tissue that form lumps within the thyroid gland, while thyroid cysts are fluid-filled nodules. Essentially, a thyroid cyst is a specific type of thyroid nodule that contains fluid rather than solid tissue.
Key Differences and Similarities
- Thyroid nodules can be completely solid, completely fluid-filled (pure cysts), or partially solid and partially fluid-filled (complex or mixed nodules) 1.
- Pure cysts are almost always benign, while solid nodules have a higher risk of being cancerous, though still most are benign.
- When evaluating thyroid nodules, doctors typically use ultrasound to determine their composition and may perform fine needle aspiration (FNA) to collect cells for analysis if the nodule has suspicious features.
Diagnosis and Treatment
- Treatment depends on whether the nodule causes symptoms, its size, and if there's concern for cancer, ranging from monitoring with regular ultrasounds to surgical removal in some cases.
- The overall rate of thyroid cancer, particularly papillary carcinoma (PTC), in patients with TNs is less than 3%–5% 1.
- Given the generally favorable prognosis of PTC and its lower frequency among patients with TNs, population screening with neck US is not recommended by WHO.
Clinical Recommendations
- Thyroid cysts and nodules should be evaluated based on their composition and suspicious features, rather than their size alone.
- Fine needle aspiration cytology (FNAC) should be performed in any thyroid nodule >1 cm and in those <1 cm if there is any clinical or ultrasonographic suspicion of malignancy 1.
- The use of various immunohistochemical markers in cytologic samples to differentiate papillary thyroid carcinoma from other follicular-derived lesions of thyroid has been explored, but none of the markers appears to be specific enough to be employed as the diagnostic marker for the cytologic diagnosis of papillary thyroid carcinoma 1.
From the Research
Definition and Distinction
- Thyroid cysts and nodules are not exactly the same, although they can be related [ 2 ].
- A thyroid nodule is a lump in the thyroid gland, which can be solid, fluid-filled (cystic), or a combination of both [ 3 ].
- Thyroid cysts are fluid-filled sacs within the thyroid gland, which can be simple or complex [ 4 ].
Characteristics and Diagnosis
- Cystic thyroid nodules can be characterized by ultrasonography, which can correctly identify cystic nodules in most cases [ 2 ].
- Fine-needle aspiration biopsy (FNAB) is a diagnostic tool used to evaluate thyroid nodules, including cystic ones [ 5 ].
- Ultrasound-guided FNAB can increase the accuracy of diagnosis for cystic thyroid nodules [ 5 ].
Treatment and Management
- The management of thyroid cysts and nodules depends on their characteristics, size, and the patient's overall health [ 3 ].
- Simple aspiration or sclerotherapy with tetracycline hydrochloride can be effective in treating thyroid cysts [ 6 ].
- Surgical removal may be necessary for large or suspicious nodules, including those with malignant potential [ 2 ].