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Cytojournal. 2017 Apr 28;14:10. doi: 10.4103/1742-6413.205313. eCollection 2017.

Cytomorphologic features distinguishing Bethesda category IV thyroid lesions from parathyroid.

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Address: Department of Pathology and Laboratory Medicine, Weill Cornell Medical Center, New York, NY 10065, USA.
Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY 10032, USA.



Thyroid follicular cells share similar cytomorphological features with parathyroid. Without a clinical suspicion, the distinction between a thyroid neoplasm and an intrathyroidal parathyroid can be challenging. The aim of this study was to assess the distinguishing cytomorphological features of parathyroid (including intrathyroidal) and Bethesda category IV (Beth-IV) thyroid follicular lesions, which carry a 15%-30% risk of malignancy and are often followed up with surgical resection.


A search was performed to identify "parathyroid" diagnoses in parathyroid/thyroid-designated fine-needle aspirations (FNAs) and Beth-IV thyroid FNAs (follicular and Hurthle cell), all with diagnostic confirmation through surgical pathology, immunocytochemical stains, Afirma® analysis, and/or clinical correlation. Unique cytomorphologic features were scored (0-3) or noted as present versus absent. Statistical analysis was performed using R 3.3.1 software.


We identified five FNA cases with clinical suspicion of parathyroid neoplasm, hyperthyroidism, or thyroid lesion that had an eventual final diagnosis of the parathyroid lesion (all female; age 20-69 years) and 12 Beth-IV diagnoses (11 female, 1 male; age 13-64 years). The following cytomorphologic features are useful distinguishing features (P value): overall pattern (0.001), single cells (0.001), cell size compared to red blood cell (0.01), nuclear irregularity (0.001), presence of nucleoli (0.001), nuclear-to-cytoplasmic ratio (0.007), and nuclear chromatin quality (0.028).


There are cytomorphologic features that distinguish Beth-IV thyroid lesions and (intrathyroidal) parathyroid. These features can aid in rendering correct diagnoses and appropriate management.


Bethesda category IV; cytology; fine-needle aspiration; parathyroid; thyroid

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