Utility of fine-needle aspiration cytology in the identification of parathyroid lesions

OBJECTIVES: Fine-needle aspiration cytology (FNAC) is a first-line investigation in the evaluation of neck nodules. In an attempt to search for reliable cytomorphological criteria for parathyroid lesions, we systematically evaluated cytomorphology of FNAC of parathyroid lesions. STUDY DESIGN: FNAC of 15 parathyroid and 15 hyperplastic thyroid nodules with histological confirmation were reviewed for following features: Cellularity, follicles, bare nuclei, cohesiveness, vascular profiles, cytoplasmic granularity, intracytoplasmic vacuolation, mitosis, macrophages, and colloid. RESULTS: Vascular proliferation, bare nuclei, intracytoplasmic fat vacuolation, absence of colloid, and high cellularity showed significant association with parathyroid lesions (P ≤ 0.05). Intracytoplasmic fat vacuolation was 53.3% sensitive and 100% specific for parathyroid. Follicular pattern and papillaroid clusters were also important; however, they achieved nearly significant statistical difference (P = 0.05 and P = 0.06, respectively). The combination of vascular proliferation and intracytoplasmic fat vacuolation were significantly associated with parathyroid (P = 0.006) whereas the absence of bare nuclei and the presence of background colloid were associated with thyroid cytomorphology (P = 0.03). CONCLUSION: No single cytological feature is helpful in differentiating parathyroid from thyroid lesion. Vascular proliferation, bare nuclei, intracytoplasmic fat vacuolation, high cellularity, and the absence of colloid were significantly associated with the parathyroid origin. The combination of at least two features — vascular proliferation and intracytoplasmic fat vacuoles — were highly suggestive of parathyroid origin.