Cytology of the thyroid gland: pitfalls in aspiration of the fibrotic nodule.

Fibrotic changes can be found in a variety of pathologic processes that affect the thyroid gland, and yet fine-needle aspiration (FNA) correlation of these lesions is not well-known. Cytologic findings are described from three different lesions, all with extensive fibrosis, that occurred in thyroid gland FNA. In each case, fibrotic changes resulted in cytologic changes potentially representing pitfalls in aspiration diagnosis. FNA revealed, solely or predominantly, fibroblasts in 2 patients whose subsequent thyroidectomies disclosed diffusely sclerotic papillary carcinoma and multinodular goiter. In the third case, an initially suspicious FNA was followed by multiple unsuccessful attempts at a second FNA. At thyroidectomy, a follicular adenoma with post-FNA fibrosis and infarction was identified. The differential diagnoses in thyroid FNA of fibrotic nodules can be broad, and this is discussed. Awareness of potential pitfalls may improve diagnostic accuracy.