A 72 year old woman presented with swelling of the right lobe of her thyroi
d gland. Fine needle aspiration and flow cytometry showed a clonal populati
on of B cells expressing CD10 and a diagnosis of follicle centre cell lymph
oma was made. Subsequent excision of the thyroid showed the typical histolo
gical features of a marginal zone non-Hodgkin lymphoma. Polymerase chain re
action showed no evidence of t (14;18). Immunohistochemistry confirmed CD10
positivity and LN1 (CDw75) expression. This is only the second report of a
berrant expression of CD 10 by a marginal zone lymphoma.