Black thyroid.A finding of a black thyroid gland (figure 1) is unusual and disconcerting. Among the possible causes of black thyroid are minocycline-induced pigmentation, hemochromatosis hemochromatosis /he·mo·chro·ma·to·sis/ (-kro?mah-to´sis) a disorder of iron metabolism with excess deposition of iron in the tissues, bronze skin pigmentation, cirrhosis, and diabetes mellitus.hemochromatot´ic he·mo·chro·ma·to·sis (h, ochronosis, mucoviscidosis, ceroid storage disease, bruising, and hemorrhage. In addition, medullary thyroid carcinomas have been reported to produce melanin in rare cases. Minocycline, a derivative of tetracycline, can also cause pigmentation in the skin, nails, oral mucosa, teeth, eyes, bones, cardiac valves, coronary vessels, substantia nigra, and atherosclerotic plaques. In the thyroid, minocycline accumulates in the follicular fol·lic·u·lar (f  -l k y-l epithelium and colloid 1. glutinous or resembling glue. 2. a chemical system composed of a continuous medium (continuous phase) throughout which are distributed small particles, 1 to 1000 nm in size (disperse phase), that do not settle out under the influence of gravity; the particles may be in emulsion or in suspension. The term may be used to denote either the particles or the entire system. in benign, and even hyperplastic tissue as a result of the oxidative interaction between the drug and the enzyme thyroid peroxidase (figure 2). These black pigment deposits remain in epithelial cells for long periods of time. [FIGURE 1 AND 2 OMITTED] Ultrastructurally, pigment (neuromelanin) is confined to lysosomes. This granular pigment stains like melanin on Fontana-Masson staining; it can also be bleached. In aspiration cytology aspiration biopsy cytology (ABC) the microscopic study of cells obtained from superficial or internal lesions by suction through a fine needle. exfoliative cytology microscopic examination of cells desquamated from a body surface or lesion as a means of detecting malignancy and microbiologic changes, to measure hormonal levels, etc. Such cells are obtained by aspiration, washing, smear, or scraping. specimens, the degenerative changes in follicular epithelial ceils found in black thyroid glands can cause nuclear hyperchromatism and chromatin sex chromatin Barr body; the persistent mass of the inactivated X chromosome in cells of normal females. chro·ma·tin (kr  m clumping (figure 3). Pigment present in follicular epithelial cells in fine-needle aspirate as·pi·rate ( sp-r t can also be mistaken for hemosiderin hemosiderin /he·mo·sid·er·in/ (he?mo-sid´er-in) an insoluble form of tissue storage iron, visible microscopically both with and without the use of special stains.he·mo·sid·er·in (h  -laden macrophages. It is interesting that thyroid adenomas adrenocortical adenoma a benign tumor of the adrenal cortex, usually small and unilateral; most types cause endocrine symptoms. basal cell adenoma a benign, encapsulated, slow-growing, painless salivary gland tumor of intercalated or reserve cell origin, occurring mainly in males, in the parotid gland or upper lip; solid, canalicular, trabecular-tubular, and membranous and carcinomas fail to incorporate black pigment (figure 1). Although the concentration of minocycline-related pigment can interfere with thyroid function, it appears to be unrelated to tumorigenesis. Pigment-containing follicular epithelium has reduced thyroglobulin and ubiquitin immunoreactivity. Because of the possible antithyroid antithyroid /an·ti·thy·roid/ (-thi´roid) counteracting thyroid functioning, especially in its synthesis of thyroid hormones. effects of minocycline, it seems advisable to monitor thyroid function in patients who are on long-term minocycline therapy. [FIGURE 3 OMITTED] Suggested reading Bell CD, Kovacs K, Horvath E, Rotondo F. Histologic, immunohistochemical, and ultrastructural findings in a case of minocycline associated "black thyroid." Endocr Pathol 2001;12:443-51. Keyhani-Rofagha S, Kooner DS, Landas SK, Keyhani M. Black thyroid: A pitfall for aspiration cytology. Diagn Cytopathol 1991;7:640-3. Thompson AD, Pasieka JL, Kneafsey P, DiFrancesco LM. Hypopigmentation of a papillary carcinoma arising in a black thyroid. Mod Pathol 1999;12:1181-5. From the Department of Pathology, Beth Israel Deaconess Medical Center, Boston. |
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