Papillary thyroid cancer in black thyroid: a case report and literature review

BACKGROUND: Black thyroid is a rare incidental finding during surgery. We report the case of a patient with papillary thyroid cancer who was incidentally found to have minocycline-induced black thyroid. CASE DESCRIPTION: A 29-year-old woman presented with a left thyroid nodule and metastatic papillary thyroid cancer involving the left neck level IV lymph nodes. She had a medical history of anxiety disorder with depression, severe acne, and rosacea, and had been taking benzodiazepines, selective serotonin reuptake inhibitors, isotretinoin, and minocycline for a few years. The patient underwent a total thyroidectomy with left central compartment neck dissection and ipsilateral modified radical neck dissection. A black thyroid gland was identified during thyroidectomy. During level IV dissection, we noticed a similar black discoloration in the adipose tissue of the lower neck. Pathological examination revealed brown pigmentation with few macrophages on several foci of the thyroid parenchyma. Brown pigmentation was not identified in the thyroid tumor, metastatic and normal lymph nodes, or background adipose tissue. CONCLUSIONS: We report a case of papillary thyroid microcarcinoma with cervical lymph node metastases in a black thyroid. The clinical findings were consistent with those of previous reports. Based on the literature, it remains unclear if this minocycline triggered finding is associated with an increased frequency and/or aggressiveness of thyroid carcinomas. In the absence of adequate evidence, prolonged minocycline users should ideally undergo routine thyroid assessment to identify possible malignancy.