Follicular-patterned thyroid lesions

Aim: Our aim is to determine the minimal cytopathologic criteria needed to make differential diagnosis in follicular-patterned lesions of the thyroid gland. Materials and Methods: We reviewed 56 fine needle aspiration cytology specimens which were reported as "suspicious for follicular-patterned lesions of thyroid" between years 2001 and 2005 in our hospital and their histological slides. Parameters for cytopathologic assesment are cellularity, colloid formation, multilayered rosette formation, follicular cell rings, monolayered sheets, intact follicles, hyperplastic papillae, hyaline stromal fragments, intranuclear inclusions, nuclear grooves, angulated nuclei, nucleoli, cerebriform nuclei, nuclear size, macrophages, flame cells and Hurthle cells. Statistical analysis was performed using %(2) and Fisher's-exact tests and Kolmogorov-Simirnov test. Results: Four cytopathologic features-cerebriform nuclei, angulated nuclei, nuclear grooves and intranuclear inclusion-were constantly observed in the follicular variant of papillary carcinoma (p< 0.05). Diluted colloid, monolayered sheet, nuclear size, macrophage and nucleoli were frequently seen in nodular hyperplasia (p< 0.05). The nuclear size was the sole differential cytopathologic criteria between follicular adenoma and follicular carcinoma (p< 0.05). Conclusion: Detailed cytopathologic examination was found to be important in differentiating follicular variant of papillary carcinoma from nodular hyperplasia. On the other hand, none of the cytopathologic findings were sufficient to distinguish follicular adenoma from follicular carcinoma. Therefore, cytopathologists should report such lesions as "follicular neoplasms".