Most thyroid fine-needle aspirates fit neatly into one of the 6 categories of the Bethesda classification. But sometimes, cases are not so easy and it is worth thinking outside the boxes!
This case was one of the latter. Although the targeted nodule was located in the thyroid gland in a patient with a history of thyroid nodules, something didn’t quite fit. While the fragments were very large, they did not appear to be organized in a usual pattern for thyroid epithelial cells, nor did they have nuclear changes suggestive of malignancy that would explain their “disorganization”.
The background was not so helpful either; looking for clear lymphocytes or oncocytes that would point to a specific diagnosis were sadly lacking.
What was helpful was a review of the chart, which revealed hyperparathyroidism! Sure enough, immunostaining on the cell block confirmed that the cells were positive for GATA3, proving a parathyroid lineage (despite intrathyroidal localization).
Sampling of parathyroids by fine-needle aspiration is usually unintentional. As a consequence, it is rare, and when it does occur, it is often unsuspected! The morphology and architecture can mimic thyroid lesions almost to perfection, so the key is often to obtain better clinical information.
Acknowledgments
Many thanks to Dr. Manon Auger for sharing this case.