ODP508 PRIMARY DIFFUSE LARGE B-CELL THYROID LYMPHOMA: A CASE REPORT

BACKGROUND: Primary thyroid lymphoma (PTL) is a rare disease, accounting for <5% of all thyroid malignancies. Diffuse B-cell lymphoma (DBCL) is the most common type of PTL. The diagnosis and management of PTL depends on the histopathologic results. CLINICAL CASE: A 77-year-old female (with T2DM, Hypertension and CAD) had sudden onset of rapidly enlarging neck mass associated with compressive symptoms such as dyspnea, dysphagia and hoarseness of voice. She underwent neck CT scan with contrast revealing a heterogenous mass on right thyroid lobe 9.7×6.9×5.5 cm, with encasement and invasion of adjacent portions of trachea and right common carotid artery . Thyroid function tests were normal and anti-TPO was elevated at 1891.76 IU/ml (NV: < 5.6 IU/mL). Patient underwent tracheostomy and excision biopsy of the mass. Histopathologic report showed atypical lymphoid proliferation and Hashimoto's thyroiditis. Immunohistochemical staining of the neoplastic cells were reactive to CD20, CD3; and Ki67 was positive in 70-90%. Fluorescence in situ hybridization test for c-myc, BCL 6 rearrangement and IGH/BCL 2 fusion for ruling out aggressive double-hit lymphomas came out negative, hence the final diagnosis of Non-Hodgkin's Diffuse Large B-cell Lymphoma. Most PTL originate from B cells, especially DBCL, which accounts for 50–80%. A standard management in PTL is controversial due to limited clinical trials and due to its heterogenous nature. A multidisciplinary approach is the best management technique for PTL. Chemotherapy can cause remission but recent studies showed better response with chemoradiotherapy. The patient was started on R-CVP (rituximab, cyclophosphamide, vincristine, prednisolone). One year after, FDG-PET showed resolution of right thyroid lobe mass with mild diffuse metabolic activity in the rest of thyroid gland, and absence of hypermetabolic lymph nodes. CONCLUSION: In older patients presenting with a rapidly enlarging goiter, especially in a setting of Hashimoto's thyroiditis, the diagnosis of PTL should be considered and differentiated from other types of thyroid disease. The prognosis and management of PTL differ from secondary thyroid lymphoma and other types of neoplasm. It can have a good outcome when recognized in earlier stages and if with less aggressive histopathologic type. Presentation: No date and time listed