This is a rare case report of Hashimotoís thyroiditis in a patient with MALT thyroid lymphomas. The patient presented with an enlarged neck mass over the past 10 years and had rapidly enlarged neck mass with compressive symptoms for about 2 months. Examination by an endocrinologist found that the size of the thyroid gland was 120 gm with firm consistency and with no tenderness. She had clinical hypothyroidism and no abnormality of neither lymphadenopathy nor any masses. She was diagnosed with Hashimotoís thyroiditis because her thyroids function lest showed primary hypothyroidism [(FT4 = 0.76 ng/dl (0.93-1.71), FT3 = 1.76 pg/ml (1.8-4.6), TSH = 8.24 mIU/L (0.27-4.21)] with antimicrosomal antibody positive titers (> 1:409,600): Diagnosis of primary thyroid lymphoma was diagnosed by FNA and total thyroidectomy was performed. About 1 day after total thyroidectomy, she developed clinical hypocalcemia and the laboratory showed that calcium was = 6.2 ng/dl (8.5-10.1), phosphorus = 6.4 mg/dl (2.5-4.9). After 10% calcium gluconate replacement, her hypocalcemic symptoms didnít appear and she received oral replacement of calcium carbonate and vitamin D before discharge. During OPD follow up, her pathological report from Maha Chakri Sirinthorn Medical Center was a diagnosis of Non Hodgkinís lymphoma, low grade and the latter 1 week immunohistochemically staining of tumor markers indicated B-cell type (CD20) with MALT (AE1/AE3) lymphoma. Staging of the disease was stage IE and she received one course of CHOP (Cyclophosphamide, doxorubicin, vincristin and prednisolone). After one course of CHOP regimen, she was healthy and the hematologist ordered two courses of CHOP and external radiation.

Keywords: Thyroid lymphoma / Hashimotoís thyroiditis