Background : Riedel's thyroiditis (RT) is a rare fibrosclerotic disease that affects the thyroid gland and surrounding tissues. The etiology is unknown, and it rarely affects the elderly.
Case Presentation : A 56-year-old man, with no particular medical history, was seen in consultation at the Surgery Department of the Treichville Teaching University Hospital for a painless swelling of the anterior base of the neck. Physical examination showed a patient with inspiratory dyspnea probably due to tracheal compression. The patient underwent a subtotal thyroidectomy because of the clinical symptomatology and the persistence of dyspnea. Macroscopically, the thyroid mass was well-encapsulated, weighed 80g, and measured 10 cm x 5 cm x 2 cm. After section, we observed whitish fibrous nodules associated with pinkish-brownish band. Histologically, the architecture of thyroid tissue was restructured by dense and diffuse collagenous fibrosis in which rare atrophic thyroid vesicles were found. The fibrous areas were infiltrated by inflammatory elements, including lymphocytes, plasmocytes, and eosinophilic polynuclear cells. No malignant cells were found. Masson's trichrome staining confirmed the fibrous nature of the thyroid tissue, which is essential for the certain diagnosis of Riedel's thyroiditis. There was no postoperative complication
Conclusion : Riedel's thyroiditis is a rare disease that is difficult to diagnose preoperatively despite advances in imaging and fine needle cytology screening methods. Histological examination of the sample confirms the diagnosis of Riedel's thyroiditis. Thyroidectomy is indicated in patients with compression symptoms. Clinicians should suspect Riedel's thyroiditis in patients with a hard thyroid mass with compressive symptoms, despite its rarity.