Differential Diagnosis for Thyroid Nodule
- Single most likely diagnosis
- Benign thyroid cyst or colloid nodule: The presence of a hypoechoic/predominantly cystic nodule with echogenic foci and comet tail artifact, suggestive of colloid, points towards a benign thyroid lesion. The lack of vascular flow within the focus by Doppler further supports this diagnosis, as malignant lesions often exhibit increased vascularity.
- Other Likely diagnoses
- Thyroid adenoma: Although less likely than a benign cyst or colloid nodule due to the cystic appearance, a thyroid adenoma could present with variable echotexture and may contain cystic components.
- Hemorrhagic thyroid cyst: The presence of a cystic nodule with echogenic foci could also represent a hemorrhagic cyst, especially if the patient has a history of trauma or sudden onset of pain.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Papillary thyroid carcinoma: Although the ultrasound characteristics are not highly suggestive of malignancy, papillary thyroid carcinoma can occasionally present as a cystic lesion. The presence of echogenic foci with comet tail artifact does not rule out malignancy, and biopsy may be necessary to confirm the diagnosis.
- Medullary thyroid carcinoma: This rare malignancy can also present as a cystic or hypoechoic nodule, and its diagnosis is crucial due to its potential for aggressive behavior and association with multiple endocrine neoplasia syndromes.
- Rare diagnoses
- Thyroglossal duct cyst: Although typically midline, a thyroglossal duct cyst could potentially present as a lateral neck mass and may contain echogenic debris or exhibit a cystic appearance on ultrasound.
- Parathyroid cyst: A parathyroid cyst could mimic a thyroid cyst or nodule on ultrasound, but its location and the presence of parathyroid hormone within the cyst fluid could help differentiate it from a thyroid lesion.