Primary Mucosa-Associated Lymphoid Tissue Lymphoma of Thyroid with the Serial Ultrasound Findings

Abstract

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) of the thyroid gland is uncommon. Even though its natural history is not well defined, it is known to be indolent course. We present a case of primary MALT thyroid lymphoma with the serial sonographic findings in the patient presenting as the focal nodule. A 45-year-old woman visited our hospital for neck examination. Initially, fine-needle aspiration cytology in the focal hypoechoic lesion in the left thyroid lobe on ultrasound sonography was performed and consistent with Hashimoto's thyroiditis. However, the results of serial ultrasounds and core-needle biopsy revealed an extranodal marginal zone lymphoma of MALT on 4-year follow-up. Patients with a focal hypoechoic nodule with linear echogenic strands and segmental pattern in the background of Hashimoto's thyroiditis on ultrasonography should undergo careful surveillance for malignancy. Serial sonographic features in this case are meaningful in the understanding of the natural history of the extranodal marginal zone lymphoma of MALT of the thyroid.

Figure 1

(a) Thyroid ultrasound shows a markedly hypoechoic area (arrow), with interspersed linear echogenic strands pattern in transverse view and (b) longitudinal view. (c) Color Doppler image shows a left thyroid nodule with peripheral increased blood flows in longitudinal view during a first visit.

Figure 2

Four years later, image of the left thyroid nodule (a) in transverse view and (b) longitudinal view.

Figure 3

(a) Neck computed tomography shows 1.9 × 1.2 cm sized hypodense mass involving thyroid isthmus in the left thyroid. (b) Thyroid scan with Tc-⁹⁹m pertechnetate shows diffuse and even uptake in both thyroid glands.

Figure 4

(a) Microscopic finding shows the extranodal marginal zone lymphoma of MALT in a background of Hashimoto's thyroiditis (H&E stain, ×20). (b) Microscopic finding of the thyroid mass shows marked lymphocytic infiltration and a few degenerated follicles (H&E stain, ×200). (c) Immunohistochemical findings disclose diffuse positive staining for CD20 (immunohistochemistry, ×200). (d) Immunostaining for cytokeratin highlights lymphoepithelial lesions (immunohistochemistry, ×200).