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Black thyroid: a pitfall for aspiration cytology
S Keyhani-Rofagha1, D S Kooner, S K Landas
1Department of Pathology, Ohio State University, College of Medicine, Columbus 43210.
Diagnostic Cytopathology
|January 1, 1991
Summary
Minocycline can cause black thyroid discoloration, mimicking cancer on fine-needle aspiration cytology. Pathologists must consider this drug side effect to avoid misdiagnosis.
Area of Science:
- Pathology
- Endocrinology
- Pharmacology
Background:
- Minocycline, a tetracycline antibiotic, has been associated with black thyroid discoloration.
- Fine-needle aspiration cytology (FNAC) is increasingly used for thyroid lesion diagnosis.
Observation:
- This report details a second case of black thyroid preceded by FNAC.
- Thyroidectomy was performed in both cases due to indeterminate FNAC findings.
Findings:
- Degenerative changes in follicular cells can mimic neoplasia (nuclear hyperchromasia, chromatin clumping).
- Pigment deposition in thyroid cells and macrophages can be obscured by other pigments like hemosiderin.
- Special stains (Melanin stain, potassium permanganate) confirm the pigment's nature.
Implications:
- A history of tetracycline use is crucial for pathologists to consider black thyroid.
- Awareness of this pitfall is important given the rise in FNAC and tetracycline use.
- Accurate diagnosis prevents unnecessary thyroidectomies for this benign condition.