|LETTER TO THE EDITOR
|Year : 2012 | Volume
| Issue : 2 | Page : 71-72
Follicular adenoma of thyroid with black pigmentation
Prerna Arora1, Seema Rao1, Nita Khurana1, Anoop Raj2
1 Department of Pathology, Maulana Azad Medical College and Associated Hospital, New Delhi, India
2 Department of ENT, Maulana Azad Medical College and Associated Hospital, New Delhi, India
|Date of Web Publication||12-May-2012|
Department of Pathology, Maulana Azad Medical College, New Delhi - 110 002
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Arora P, Rao S, Khurana N, Raj A. Follicular adenoma of thyroid with black pigmentation. Thyroid Res Pract 2012;9:71-2
Black pigmentation of thyroid gland is a rare and poorly recognized entity. It is usually associated with chronic minocycline therapy, and less commonly with hemochromatosis, ochronosis, mucoviscidosis, ceroid storage disease, bruising, and hemorrhage.  We report black pigmentation in follicular adenoma as incidental finding in a 55-year-old female.
Our patient presented with gradually progressive swelling in the neck for two years with history of chronic constipation. Thyroid function tests fell within normal limits. Fine needle aspiration cytology (FNAC) suggested cystic colloid goiter. Peroperatively, thyroid was multinodular. Total thyroidectomy was performed and the specimen revealed multiple colloid-filled cysts along with a well-circumscribed, grey brown nodule in isthmic region measuring 2.5 × 2.0 × 1.5 cm. Microscopic examination of bilateral thyroid lobes revealed cystic colloid goiter [Figure 1]a. Sections from the isthmic nodule showed features of follicular adenoma [Figure 1]b. In addition, there was presence of clumps of intracytoplasmic golden brown pigment in adenoma cells [Figure 2]a. The pigment was positive with Masson fontanna [Figure 2]b and negative with Perl's stain. Pigment was confined to the adenoma only and surrounding parenchyma showed no such pigment. Thus, a final diagnosis of black adenoma on a background of colloid goiter was made. In the present case, no evident cause of pigmentation was found.
|Figure 1a: Thyroid revealing features of cystic colloid goiter (H and E, x10)|
Figure 1b: Isthmic nodule showed follicular adenoma thyroid (H and E, x20)
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|Figure 2a: Clumps of intracytoplasmic golden brown pigment in adenoma cells (H and E, x40)|
Figure 2b: Pigment showed positivity with Masson fontana (H and E, x60)
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Thyroid gland with black pigmentation has mostly been observed as incidental and autopsy finding as there is no associated disturbance in thyroid function. However, it is reported in association with tumors like hyalinizing trabecular adenoma,  follicular adenoma,  follicular carcinoma,  and papillary carcinoma.  Thus, recognition of black thyroid necessitates serious consideration of coexistent malignancy.
Of additional interest in the present case was presence of pigment confined to adenoma cells only. To the best of our knowledge, only single study by Koren et al., reported similar features, and hypothesized hyper-functioning of adenoma as a cause of selective pigmentation.  Remaining publications in literature had shown either selective pigmentation of the adjacent thyroid gland without any pigmentation of the adenoma  or no distinctive difference in the pigmentation between the adenoma and the surrounding thyroid gland.  Moreover, few authors have emphasized that the presence of hypopigmented focus in a black thyroid heralds thorough pathological examination as such foci are known to be associated with a higher incidence of developing malignant change.  It is postulated that there is diminished function of thyroid peroxidase in carcinomatous area resulting in failure to incorporate pigment. In the present case, unusual functional divergence between neoplastic and non-neoplastic tissues needs further explanation for the possible pathogenesis.
Despite increasing use of FNAC and large number of patients who receive tetracycline, there are too few reports on FNAC of black thyroid, which may either be due to lack of awareness or the pigment getting obscured by other pigments such as hemosiderin.
In conclusion, presence of brown-black pigment in FNA smears, especially in follicular cells, should alert the cytopathologist for possibility of Black thyroid. Incidental discovery of black thyroid deserve thorough pathological examination with serial sectioning to avoid missing coexistent malignancy.
| References|| |
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[Figure 1], [Figure 2]