Clinicopathological characteristics of methotrexate-related lymphoproliferative disorder of the thyroid: A study of 11 patients.

Methotrexate (MTX) is a well-known agent that can potentially cause lymphoproliferative disorder (LPD), known as MTX-related LPD (MTX-LPD). Only two cases of thyroid MTX-LPD have been reported to date. This study aimed to report 11 cases of MTX-LPDs arising in the thyroid gland and discuss their clinicopathological characteristics. Of the 747 patients with cytologically suspected lymphoma, 11 had received MTX. The mean age of the patients with MTX-LPD was 70.2 years (range: 51-82 years), and all were female. The duration of MTX administration ranged from 5 to 31 years (mean: 19.5 years). Nine patients (81.8 %) tested positive for anti-thyroglobulin antibody and/or anti-thyroid peroxidase antibody. In three patients, the tumor decreased in size or disappeared without surgery or chemotherapy after withdrawal of MTX therapy. Histologically, all eight nodules examined were B-cell lymphomas, and seven were mucosa-associated lymphoid tissue (MALT) lymphomas. Epstein-Barr virus-encoded small RNA in situ hybridization showed negative results for all six nodules examined. All five patients who were followed-up at our hospital exhibited progression-free survival for >3 years without chemotherapy. Six patients were transferred to other hospitals, and their follow-up details are unknown. MTX-LPDs occurring in the thyroid are characterized by a high female predominance, positivity for anti-thyroid autoantibodies, high prevalence of MALT lymphomas, negativity for Epstein-Barr virus, and good outcomes without chemotherapy. We recommend that patients with thyroid lymphoma should be checked for a history of MTX.