Can cytomorphology differentiate between benign nodules and tumors arising in Graves' disease?

Fine-needle aspiration (FNA) specimens from thyroid nodules arising in Graves' disease (GD) can pose diagnostic difficulties because the cytomorphologic changes in GD may mimic nuclear features of papillary thyroid carcinoma (PTC). In addition, treatment of GD patients with radioactive iodine (RAI) may cause significant cytologic atypia, further increasing the diagnostic difficulty. From March 1999 to April 2002, a total of 14 hypofunctioning nodules in 9 patients with GD underwent FNA; 3 patients had received RAI treatment. Three cases were diagnosed as suspicious for PTC and 11 as benign. Three patients with the diagnosis of suspicious for PTC on FNA underwent surgery and were found to have papillary carcinoma. We assessed all cases to find key cytologic features that can differentiate between nodules with reactive/reparative nuclear atypia from PTC arising in GD. The cytologic features assessed included cellularity, amount of colloid, monotony of the cell population, oncocytic features, cell crowding, lymphocytic infiltration, nuclear elongation, nuclear grooves, pale powdery chromatin, presence of small eccentric nucleoli, and random nuclear atypia. Each feature was semiquantitatively graded on a sliding scale of 0 to 4, with 0 representing absence and 4 representing a predominance of the feature. The mean value of each feature was calculated and the benign and malignant lesions were compared using the unpaired t-test. Four features were found to be statistically significant in the diagnosis of PTC as compared to the benign nodules in GD. The nuclei of PTC in GD show prominent nuclear elongation, pale powdery chromatin, intranuclear grooves, and small eccentric nucleoli. All other features studied were not found to be statistically significant. There does exist an overlap between the cytologic features of benign nodules and PTC arising in GD. However, adherence to strict diagnostic criteria (nuclear elongation, pale powdery chromatin, intranuclear grooves, and small eccentric nucleoli) can enable the diagnosis of PTC arising in GD.