Drug-induced thyroiditis and papillary carcinoma in a minocycline-pigmented black thyroid gland.

We describe a 31-year-old woman who had ingested minocycline for 18 months prior to presenting with hyperthyroidism and a palpable thyroid nodule. There was no evidence of Graves' disease or autonomous nodule on thyroid scintigraphy, and a clinical diagnosis of thyroiditis was made. Fine-needle aspiration biopsy of the palpable lesion suggested papillary carcinoma, and the patient underwent a total thyroidectomy. Intraoperatively, the thyroid gland was found to have a striking black discoloration. Subsequent histological examination revealed the accumulation of pigment globules within the apical cytoplasm of the follicular cells, and associated findings of a drug-induced thyroiditis. The tumor nodule showed features of infarction and was felt to represent a necrotic papillary microcarcinoma. We postulate that in addition to causing black thyroid pigmentation, chronic minocycline use in our patient resulted in thyroiditis and subsequent hyperthyroidism. The papillary microcarcinoma was probably a coincidental finding.