What is the best diagnosis here?
A 41-year-old woman presents with a sensation of “fullness” in her neck for the past few years. She also feels “nervous and jittery” for several days at a time, reports occasional insomnia, and has frequent bowel movements (5–7 times a day). She denies heat intolerance. Ultrasound-guided fine needle aspiration of thyroid.

Lymphocytic thyroiditis

The smears display numerous cellular aggregates and single cells seen at low power. High power reveals a mixed lymphocytic population scattered among Hurthle cells. The Hurthle cells have large round nuclei, prominent nucleoli, abundant cytoplasm, and rare mitotic figures. The abundant discohesive lymphocytic population is highly suggestive of an inflammatory lesion; one should be cautious about diagnosing carcinoma based on atypia seen with a prominent inflammatory background. The colloid to epithelium ratio would be much higher in an adenomatoid nodule. In follicular neoplasms, one would find more epithelial cells arranged in microfollicles without the inflammatory component seen here. Finally, medullary carcinomas typically have an abundance of cells with neuroendocrine (salt-and-pepper) nuclei, occasional plasmacytoid and spindled features, and associated amyloid. Subsequent thyroidectomy showed a multinodular hyperplasia with chronic lymphocytic thyroiditis (Hashimoto thyroiditis). References 1.Harvey AM, Truong LD, Mody DR. Diagnostic pitfalls of hashimotos/lymphocytic thyroiditis on fine-needle aspirations and strategies to avoid overdiagnosis. Acta Cytol. 2012;56(4):352360. 2.Baloch ZW, Cibas ES, Clark DP, et al. The national cancer institute thyroid fine needle aspiration state of the science conference: a summation. CytoJournal. 2008;5(1):6.