Abstract: Background and purpose: Primary thyroid lymphoma (PTL) is uncommon in clinic with quite different treatment from that of other malignant thyroid tumors. Therefore, to achieve complete understanding of PTL has crucial significance. This study aimed to investigate the clinical and computed tomography (CT) characteristics of PTL. Methods: The clinical and imaging data from 22 patients with PTLs confirmed by pathology were collected. The clinical symptoms of patients, the site, size, shape, margin, CT value and enhancement pattern, relation with surrounding tissues of PTLs and cervical lymph nodes were summarized retrospectively. Results: All the 22 patients including 8 males and 14 females had an average age of 60 years (range: 39-77 years). Twelve PTLs rapidly progressed in short term and the rest expanded slowly. The tumors involved bilateral thyroid in 11 cases, unilateral thyroid in 8 cases and both right lobe and isthmus in the remaining 3 cases. The long and short ranges were (12-104) mm and (11-71) mm. The solitary, multiple and diffuse nodules distributed in 5, 5 and 12 patients, respectively. In axial plain CT scans, low density appeared in 15 patients, isodensity in 7 patients, calcification inside the lesion in 0 patient, and necrosis in 5 patients. Nineteen PTLs manifested slight or moderate enhancement, and 3 marked enhancement in contrast-enhanced axial CT images. Homogeneous density and mixed density were demonstrated in 13 and 9 cases, respectively. Trachea and esophagus was pushed in 17 and 5 cases, tumors were involved into superior mediastinum in 12 cases and enlarged lymph nodes were demonstrated in 8 cases. Conclusion: If a solid thyroidal mass in an old female patient rapidly progresses in short term and CT scans show homogeneous and low density, slight or moderate enhancement, and diffusive swelling with compression and invasion of surrounding tissues, it has a high possibility of PTL.

Key words: Thyroid, Primary lymphoma, Clinical features, Tomography, X-ray computed