A Case of Black Thyroid Encountered during Total Thyroidectomy for Papillary Thyroid Carcinoma

Abstract

On pathological examination, minocycline-induced blackish brown pigmentation in thyroid tissue is termed black thyroid and is very rare. The patient was a 52-year-old woman treated with minocycline for about 20 years for a skin disease. A thyroid tumor was noted during follow-up after surgery for breast cancer. On thorough examination, it was diagnosed as papillary thyroid carcinoma, and total thyroidectomy and cervical lymph node dissection were scheduled. The thyroid, showing blackish brown discoloration, was observed during surgery, but the surgery was completed without changing the surgical procedure. The patient's postoperative course was favorable. On histopathological examination, the deposition of a melanin-like substance in the cytoplasm of follicular cells was observed in the non-tumorous region of the thyroid, based on which it was diagnosed as black thyroid. Black thyroid lacks clinical characteristics other than a blackish brown color, and most cases are incidentally discovered during surgery or autopsy. It is not necessary to take specific action once it is identified, but it is a rare disease, and it may not be readily diagnosed unless it is already known to be present. Thus, this case is reported along with a literature review.