Multi-institutional study of fine-needle aspiration for thyroid lymphoma

Primary thyroid lymphoma is a rare neoplasm accounting for 1% to 5% of thyroid malignancies. We study the efficacy of fine-needle aspiration (FNA) in diagnosing thyroid lymphoma.

Pathology databases from our three institutions were searched for thyroid FNA biopsies having a diagnosis of lymphoma or atypical lymphoproliferative cells, or a corresponding tissue diagnosis of thyroid lymphoma having a prior FNA biopsy.

Sixty-eight cases were retrieved from 64 patients; 67 cases with histologic confirmation. Forty-six specimens were from women (68%), ages 21 to 87 years (mean = 60). Forty-seven aspirates were diagnosed as lymphoma (n = 29) or suspicious (n = 18) for lymphoma (sensitivity = 73%), 11 atypical, 7 benign, 2 unsatisfactory, and 1 suspicious for carcinoma. Follow-up surgical diagnoses included diffuse large B-cell lymphoma (n = 43), classical Hodgkin lymphoma (5), chronic lymphocytic leukemia (5), and other cases (11). Only 12 of 64 patients (13 specimens) had a known diagnosis of lymphoma prior to FNA. Light chain restriction was detected in 34 specimens (by flow cytometry [FCM] in 32 cases or polymerase chain reaction, in 2 cases). FCM was polyclonal (n = 7) or inconclusive (2) with 25 cases not having FCM performed or not having enough viable cells for evaluation. Four cases showed lymphocytic thyroiditis on surgical follow-up with 2 of these cases having a small monoclonal lymphoid population detected by FCM.

Diffuse large B-cell lymphoma was the most common lymphoma in this series (63%). The sensitivity of FNA with the optional use of FCM was 71% with a specificity of 99%.