Endocrine Abstracts

A 60 year old Caucasian woman presented with a three month history of rapidly enlarging neck swelling and hoarseness of voice. Her past medical history included Hypothyroidism. Her neck ultrasound scans showed 3.5 cm left thyroid nodule with bilateral lymphadenopathy (U5). The Fine needle aspiration (FNA) revealed densely grouped variable sized irregular epithelial cells with nuclear atypia and spindle shaped fragments with focal areas of lymphocytic thyroiditis. The differential diagnoses included poorly differentiated thyroid cancer or a metastatic head and neck tumor. Second ultrasound scan a week later showed a marked enlargement of the mass involving the entire left lobe of thyroid extending into adjacent soft tissues and encroaching towards right side. Second FNA showed widespread lymphocytes with thick fibrous bands and infiltrates of B and T cells, suspicion of a lymphoproliferative disorder. She developed stridor and bilateral vocal cord palsy and had an urgent tracheostomy with biopsy of the neck mass. Histology showed dense fibrous tissue extending into surrounding skeletal muscles and adipose tissue with lymphocytic infiltrate and chronic inflammatory features. The lymphocytes were composed of mixed T and B cell population with plasma cells and few epithelial cells. A diagnosis of Riedel’s thyroiditis was made and the patient was started on high dose steroids. She reported a transient improvement, however the mass started to grow rapidly,prompting emergency admission. A trial of Tamoxifen was given with no benefit. CT neck revealed a marked progression of the mass compressing airways, vocal cords and left internal jugular vein, extending to the level of left oropharynx. The patient had emergency tracheostomy. Rituximab was given with some benefit. On repeat core biopsy, histology revealed atypical lymphocytes diffusely positive for CD20, CD79a, CD10, Bcl-6 and Oct-2. Ki-67 proliferation index was over 95%. This confirmed the diagnosis of large diffuse B cell lymphoma. Patient was referred for chemotherapy. This case highlights the challenges in diagnosis of Riedel’s thyroiditis and differentiating Riedel’s thyroiditis from lymphoma due to overlapping histological features and limitations of medical treatment available for Riedel’s thyroiditis.