Endocrine Abstracts

Introduction: Primary thyroid lymphomas (PTL) account for 5% of all thyroid malignancies. Treatment and prognosis depend on tumor subtype. Contrasting with diffuse large B-cell lymphomas (DLBCL), that have an aggressive clinical course and higher maximum standardized uptake value (SUVmax) in Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET), thyroid extranodal marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue (MALT) usually show an indolent course, lower SUVmax and do not require multimodal treatment. Accurate histological classification remains crucial in PTL approach.

Aim: Raise awareness for the possibility of high captation of FDG in Thyroid MALT Lymphoma (Tml) by presenting a case of TML with SUVmax of 21 in FDG-PET.

Case: A 66-year-old woman presented to the endocrine clinic due to cervical enlargement, dysphagia for solids and dyspnea with thorax anteflexion for the last four months. She denied any other symptoms. A large asymmetric multinodular diving goiter with right tracheal deviation had been firstly documented three years before. Clinically she had thyroid enlargement, multiple palpable nodules, and developed Pemberton sign. Laboratory findings included euthyroid Hashimoto Thyroiditis. Ultrasound guided fine needle aspiration (FNA) cytology of the dominant nodule (EUTIRADS-5) suggested Non-Hodgkin B Lymphoma. Two core biopsies revealed chronic lymphocytic thyroiditis with abundant B cells, suggesting PTL, which was confirmed by clonality analysis. FDG-PET revealed intense uptake exclusively in the thyroid with SUVmax of 21. Considering Ann Harbor staging IE-localized disease, and compressive symptoms, a diagnostic and potentially therapeutic total thyroidectomy was performed, with subsequent symptoms resolution and TML histologic diagnosis.

Discussion and Conclusion: PTL approach relies on accurate tumor classification. In this case, the chronic thyroiditis substract supported TML diagnosis, while the clinical course with recent compressive symptoms and SUVmax of 21 raised discomfort in postponing medical treatment in case it was a DLBCL, or TML with recent B-cells transformation, urging the need for final diagnosis. Total thyroidectomy proved to be both diagnostic and therapeutic. The clinical evolution and higher than expected SUVmax challenged final TML diagnosis.