OBJECTIVES: Ultrasound findings of primary malignant lymphoma of the thyroid were investigated among consecutive patients in a single thyroid disease center.
PATIENTS: Ninety women and 21 men diagnosed as having malignant lymphoma of the thyroid between 1998 and 2007 were investigated. Ages were 27 – 90 years, median 72 years. All patients except one were in stage IE or IIE. Diffuse large B cell lymphoma (DLBL) was diagnosed in 34 patients. Other patients had MALT lymphoma. Pathological diagnoses were made by surgical biopsies in all patients.
METHODS: Ultrasound examinations were performed with LOGIQ 500MR,
LOGIQ 700 (GE Yokogawa medical systems) or HDI5000 (Philips).
RESULTS: Lesions involved by lymphoma were demonstrated as solid hypoechoic areas without calcification. Lesions were focal in 28 patients (25.2%), spread on whole single lobe or over in 55 patients (49.6%), and involved entire glands in 28 patients (25.2%). Echogenic strands were interspersed within hypoechoic lesions in 46 patients (41.4%). In 55 patients (49.6%), swollen lymph nodes were observed in the paratracheal region or the lateral neck. Swollen lymph nodes were detected significantly less frequently in focal lymphoma (p=0.0026) and MALT lymphoma (p=0.0010). Overall sensitivity for ultrasound diagnosis of malignant lymphoma was 79.3%, while lymphoma involving entire glands had significantly lower sensitivity (35.7%, p<0.0001).
CONCLUSIONS: Characteristic appearances of malignant lymphoma of the thyroid are hypoechoic solid lesions with echogenic strands and swollen lymph nodes around the thyroid. It seems to be difficult to diagnose lymphomas involving entire glands since they resemble chronic thyroiditis in ultrasound appearances.