Papillary thyroid carcinoma in black thyroids

Black thyroid is a rare condition. It has been considered to be pathognomonic of chronic minocycline ingestion for more than 30 years, although it can also occur in patients with hemochromatosis, ochronosis, mucoviscidosis, and hemorrhage. A possible association of black thyroid with thyroid cancer has been considered, but no direct causal relationship has been established. Hence, the purpose of this article was to identify the malignant potential of such glands.

A retrospective medical chart review was performed on 433 patients who underwent thyroid surgery at Tulane University Medical Center from 2001 to 2008. Patients were grouped based on pathology: (1) benign, (2) papillary carcinoma, and (3) non-papillary thyroid carcinoma.

At surgery, 63 patients (15%) with black thyroid gland were found to have thyroid nodules. Among these nodules, 22 (35%) were benign, 21 (33%) contained papillary thyroid cancer, and 20 (32%) had a non-papillary thyroid malignancy. Nodules in black thyroids were associated with higher risk of malignancy than nodules in non-black thyroids (p = .0001). Further analysis of the papillary thyroid carcinoma group showed no statistical difference in regard to tumor size or evidence of multifocality of disease.

The finding of a black thyroid gland is unusual and disconcerting. To our knowledge, this is the first study aimed at documenting the malignant potential of black thyroid glands. This report documents that the risk of malignancy is higher in black thyroid compared to non-black thyroid glands. Furthermore, among those with papillary thyroid cancer, the presence of the pigment did not correlate with malignancy, multifocality, or tumor size.