SUN-377 - Classical Hodgkin'S Lymphoma Masquerading as Riedel'S Thyroiditis

Background:
Riedel’s thyroiditis is a rare, non-malignant, chronic inflammatory disorder of the thyroid gland. However, certain thyroid malignancies have overlapping clinical, radiographic, and histopathologic features, leading to significant diagnostic dilemmas. Lymphoma involving the thyroid is uncommon, and Hodgkin’s lymphoma in particular is rarely considered in the evaluation of a fibrosing thyroid mass.

Case:
We report a 49-year-old woman who presented with progressive neck pain, dysphagia, and an enlarging thyroid mass. Thyroid ultrasound demonstrated a 3.6 × 3.9 cm hypoechoic, lobulated isthmus nodule. Fine needle aspiration was technically difficult and initially nondiagnostic; repeat cytology was classified as Bethesda V, prompting right thyroid lobectomy and isthmusectomy. Surgical pathology demonstrated extensive acute and chronic inflammation with dense fibrosis and was interpreted as consistent with fibrosing (Riedel’s) thyroiditis. Postoperatively, the patient developed persistent neck pain and swelling requiring prolonged high-dose glucocorticoid therapy, with multiple unsuccessful taper attempts and subsequent treatment with tamoxifen. Despite therapy, she developed progressive cervical lymphadenopathy and marked leukocytosis. Review by subspecialty thyroid pathology revealed features atypical for Riedel’s thyroiditis, including absence of IgG4-related disease. Multidisciplinary evaluation with hematology-oncology raised concern for lymphoma, and subsequent second-opinion evaluation confirmed classical Hodgkin’s lymphoma.

Discussion:
This case highlights classical Hodgkin’s lymphoma as a rare but important mimic of Riedel’s thyroiditis. Progressive lymphadenopathy, steroid dependence, leukocytosis, and atypical histopathologic findings should prompt reconsideration of the diagnosis. Recognition of this entity is critical to avoid diagnostic delay and inappropriate management.

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