Thyroid neoplasia coexistent with chronic lymphocytic thyroiditis.

During a 6-year period 115 patients presenting with thyroid enlargement had evidence of chronic lymphocytic thyroiditis on fine-needle aspiration cytology. Of 27 patients in whom histological analysis was carried out, 16 had neoplasms (follicular adenoma, four; follicular carcinoma, one; papillary carcinoma, four; lymphoma, seven). Assuming that neoplasia was not overlooked in the absence of histological examination, the overall incidence was 14 per cent and that of malignant disease 10 per cent. All patients with carcinoma had cytological features suspicious of neoplasia on the first or subsequent aspirates in addition to those of thyroiditis. Cytology was suspicious of lymphoma in only two of seven patients but increasing size of the thyroid swelling was a consistent feature. Evidence of chronic lymphocytic thyroiditis may lead to neoplasia being overlooked. Repeated cytological analysis is helpful in identifying coexistent carcinoma but unreliable in excluding lymphoma.