Miller Brian Thomas, Lewis Cameron, Bentz Brandon G
Department of Surgery, Division of Otolaryngology-Head & Neck Surgery, 50 N. Medical Dr., 3C120, Salt Lake City, UT 84132, USA.
Head Neck. 2006 Apr;28(4):373-7. doi: 10.1002/hed.20385.
Black thyroid pigmentation has been considered pathognomonic for chronic minocycline ingestion for more than 30 years. Although never conclusively linked to overt disease, evidence clearly exists that minocycline is a competitive inhibitor of thyroid peroxidase in metabolically active thyroid tissue. This offers a potential mechanism of pigment accumulation, which can account for the occasional finding of hypopigmentation in thyroid carcinomas. To our knowledge, an association with tetracycline derivatives other than minocycline has not been documented.
Herein is a case report of a patient with gross black thyroid tissue containing a hypopigmented papillary thyroid carcinoma. Twelve days before surgery, the patient was placed on doxycycline, a tetracycline derivative, to optimize an in vitro fertilization regimen.
The gross specimen was diffusely black in color with a 1.5-cm hypopigmented focus of papillary thyroid cancer. Hematoxylin-eosin staining, as well as electron micrographs, was consistent with findings associated with minocycline ingestion.
Black thyroid is rare and only previously associated with chronic minocycline ingestion. This report documents a black thyroid in a patient after short-term exposure to doxycycline. Pigment accumulation in normal tissue is thought to occur by inhibition of thyroid peroxidase. Minocycline is a competitive inhibitor of this enzyme in its native configuration. Thyroid carcinomas are known to have abnormal thyroid peroxidase, which could account for reports of hypopigmented tumors within grossly darkened thyroid tissue. Hypopigmented foci within such "black thyroid" deserve through pathologic examination.
30多年来，甲状腺黑色色素沉着一直被认为是长期服用米诺环素的特征性表现。尽管从未确凿地证明其与明显疾病有关，但有明确证据表明米诺环素是代谢活跃的甲状腺组织中甲状腺过氧化物酶的竞争性抑制剂。这为色素沉着提供了一种潜在机制，这可以解释甲状腺癌中偶尔出现的色素减退现象。据我们所知，尚未有文献记载米诺环素以外的四环素衍生物与之有关联。
本文报告一例甲状腺组织呈黑色且伴有色素减退的乳头状甲状腺癌患者。手术前12天，患者开始服用四环素衍生物强力霉素，以优化体外受精方案。
大体标本呈弥漫性黑色，有一个1.5厘米大小的色素减退性乳头状甲状腺癌病灶。苏木精-伊红染色以及电子显微镜检查结果与服用米诺环素的表现一致。
甲状腺黑色色素沉着很少见，以前仅与长期服用米诺环素有关。本报告记录了一名短期接触强力霉素后出现甲状腺黑色色素沉着的患者。正常组织中的色素沉着被认为是通过抑制甲状腺过氧化物酶而发生的。米诺环素在其天然构象下是这种酶的竞争性抑制剂。已知甲状腺癌具有异常的甲状腺过氧化物酶，这可以解释在严重变黑的甲状腺组织内出现色素减退性肿瘤的报道。这种“黑色甲状腺”内的色素减退病灶值得进行全面的病理检查。
