ORIGINAL ARTICLE

Clonal B cell populations in a minority of patients with Hashimoto’s thyroiditis

A Saxena¹, E C Alport², O Moshynska¹, R Kanthan¹, M A Boctor³

¹ Department of Pathology, Royal University Hospital, Saskatoon, Saskatchewan S7N 0W8, Canada
² Department of Laboratory Medicine, Regina Qu’apelle Health Region, Saskatchewan S4T 1A5, Canada
³ Internal Medicine (Division of Endocrinology), Royal University Hospital, University of Saskatchewan, Saskatchewan, Canada

Correspondence to:
Correspondence to:
Dr A Saxena
Department of Pathology, c/o Royal University Hospital, 103 Hospital Drive, Saskatoon, SK S7N 0W8, Canada; Saxena{at}sask.usask.ca

Background: Hashimoto’s thyroiditis (HT) is a risk factor for thyroid lymphoma, and clonal B cell populations in HT support this link. The literature on B cell clonality in HT is controversial.

Aims: To identify clonal B cell populations in HT and to assess their usefulness in differentiating HT from mucosa associated lymphoid tissue (MALT) lymphoma and predicting future development of lymphoma.

Methods: DNA from formalin fixed, paraffin wax embedded blocks of thyroid specimens from 10 patients with HT and two thyroid MALT lymphomas was analysed for B cell clonality by seminested polymerase chain reaction (PCR) using FRIII/LJH and FRIII/VLJH primers to amplify the IgH gene VDJ region. In one case, PCR products were sequenced. Immunohistochemistry was performed by labelled streptavidin–biotin technique using antibodies to: CD45, CD45RO, CD3, CD20, and cytokeratin.

Results: The histopathological and clinical findings were characteristic of HT. Clonal bands were seen in three and a polyclonal smear pattern was seen in seven cases. The clonal bands in HT were associated with a background smear, and could not be reproduced from other blocks from the same case or from deeper sections of the same block. The clonal bands in thyroid lymphomas were not associated with a background smear and were reproducible. None of the patients with clonal B cells has developed malignant lymphoma during a follow up of 10–13 years.

Conclusions: B cell clonal bands in HT have different features from those in lymphoma (non-pure and non-reproducible) and do not predict future development of lymphoma.

Abbreviations: HT, Hashimoto’s thyroiditis; MALT, mucosa associated lymphoid tissue; PCR, polymerase chain reaction

Keywords: Hashimoto’s thyroiditis; clonality; immunoglobulin gene rearrangements; polymerase chain reaction; thyroid lymphoma

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