Clear nuclear changes in Hashimoto's thyroiditis. A clinicopathologic study of 12 cases.

Histologic sections of thyroid glands resected from 12 patients with Hashimoto's thyroiditis have been studied in which areas were present showing clear nuclear changes such as those seen in papillary carcinoma. The patients' ages ranged from 28 to 78 years (mean = 57.3); 11 were women and one was a man. The lesions presented as focal, ill-defined areas displaying clear nuclear changes of the cells within otherwise well-circumscribed adenomatous nodules, or as small clusters of cells showing the characteristic clear nuclear features randomly admixed with the Hashimoto's elements. Histologically, the lesions were characterized by a range of nuclear features that included optically clear nuclei, prominent cytoplasmic invaginations with intranuclear cytoplasmic inclusions, and occasional nuclear grooves. In two cases, focal papillary formations were seen that were lined by cells with optically clear nuclei. In two other cases, well-circumscribed nodules bearing the architectural features of trabecular hyalinizing adenoma with focal clear nuclear changes were also present. In three cases, small (< 0.5 cm) well-circumscribed nodules bearing cytological features indistinguishable from those of microscopic papillary carcinoma were also present in addition to the areas of clear nuclear change. Follow-up of 1.5 to 19 years (mean = 9 years) showed no evidence of recurrence or metastases in any of our patients. Our study appears to indicate that thyroid follicular epithelium in patients with Hashimoto's thyroiditis may exhibit a range of clear nuclear changes similar to those encountered in papillary carcinoma. Such changes may represent another form of response of follicular epithelium to the underlying autoimmune process with possible premalignant connotation. However, they should be interpreted in context with the rest of the findings within the involved gland to avoid an overdiagnosis of malignancy.