Neoplastic non-papillary thyroid carcinoma lesions with a fine chromatin pattern

In papillary thyroid carcinoma (PTC) in cytological and surgical specimens, fine chromatin, nuclear grooves and nuclear pseudoinclusions are the hallm arks of diagnosis. We investigated the significance of these nuclear change s in neoplastic non-PTC lesions. Fine needle aspiration biopsies (FNAB) of thyroid lesions were reviewed with histologic correlation. Twenty-five low- grade PTC and 35 neoplastic non-PTC lesions with a fine chromatin pattern i n cytology specimens were identified. These lesions were studied along with five multinodular goiters and five follicular adenomas with a coarse chrom atin pattern. The neoplastic non-PTC lesions were selected from cases with a histopathologic diagnosis of follicular neoplasm (accompanied by cytopath ologic examination) but lacking a coarse chromatin pattern. The nuclear cha nges were separated into three grades of nuclear atypia with a fine chromat in pattern, depending on the degree of nuclear enlargement and nuclear memb rane thickening, or the presence of nuclear grooves or pseudoinclusions. Th yroid lesions with a higher grade of nuclear atypia with a fine chromatin p attern were associated with larger nuclei and more readily visible nucleoli . These lesions correlated histologically with PTC and follicular adenomas with a fine chromatin pattern. The latter could be divided into three grade s: grade 1 lesions having a fine chromatin pattern similar to that of nucle i with open chromatin seen in areas of nodular goiter; grade 3 lesions havi ng nuclear features closest to those of PTC; and grade 2 lesions showing in termediate changes. In conclusion, there is a spectrum of nuclear changes i n neoplastic non-PTC lesions with a fine chromatin pattern. These lesions a re often diagnosed as follicular adenomas in surgical pathology and pose cy topathologic diagnostic problems between nodular goiter, follicular adenoma and PTC. The significance of follicular adenomas with a fine chromatin pat tern will be discussed.