Clinicopathological analysis of primary thyroid non-Hodgkin lymphoma: a single-center study

Primary thyroid lymphoma (PTL) is very rare. The aim of this study was to describe the clinical characteristics, pathological features, and survival outcomes of primary thyroid non-Hodgkin lymphoma, including the diagnostic value of clonal immunoglobulin (Ig) gene rearrangements in diagnosing mucosa-associated lymphoid tissue (MALT) lymphoma of the thyroid gland with co-existing Hashimoto thyroiditis (HT).

Paraffin-embedded tissues of patients diagnosed in our institute with PTL between 2007 and 2021 were collected. Clinicopathological features and follow-up data were retrospectively analyzed. Analysis of clonal Ig gene rearrangements were performed in patients with suspected PTL.

Of the 22 patients included in our study, 17 were female. The median age at diagnosis was 65.5 years (range, 44-80 years). We detected 11 cases of diffuse large B-cell lymphoma (DLBCL), 10 cases of MALT lymphoma, and 1 case of T-cell lymphoma. A total of 18 patients (81.8%) had early stage (I/II) disease. B-cell lymphoma showed diffuse positivity for CD20 but negative markers for thyroid-origin cells. Double-hit and triple-hit lymphomas were not found in the 8 DLBCL cases, and 2 cases of HT with lymphoid tissue dysplasia were diagnosed with MALT lymphoma with gene rearrangement testing. The median follow-up time was 47 months (range, 4-160 months), and the overall survival was 80% for MALT lymphoma (8 of 10), 72.7% for DLBCL lymphoma (8 of 11), and 100% for T-cell lymphoma (1 of 1). There was no significant difference between the groups.

PTL mostly affects middle-aged and older adult females with HT, and its main histological type is non-Hodgkin B-cell lymphoma. For patients with HT along with a histologically benign lymphoepithelial lesion, the identification of clonal Ig gene rearrangements is important for differential diagnosis. The prognosis between DLBCL and MALT is not statistically significant.