Chronic autoimmune thyroiditis (Hashimoto's thyroiditis) in patients with MALT lymphoma

Autoimmune diseases have been implicated in the genesis of MALT lymphoma of various localizations. The development of thyroidal MALT lymphoma has been described as an adverse event in patients suffering from long-standing chronic autoimmune thyroiditis (CAT, Hashimoto's thyroiditis). The percentage and possible association between CAT and extrathyroidal MALT lymphoma, however, have not been assessed so far.

A retrospective analysis of 80 patients with MALT lymphoma diagnosed and treated at our institution identified a total of 13 patients (16%) with MALT lymphoma suffering from an underlying CAT. Patient characteristics including site of disease, stage, genetic changes and clinical course were assessed and evaluated.

In total, 10 patients were female and 3 male, with the median age being 57 years (range: 31-80). Four patients suffered from thyroidal lymphoma and nine patients had extrathyroidal lymphoma (four gastric, two orbital, one small intestinal and two salivary gland lymphomas). Three patients had a long-standing history of CAT at diagnosis of MALT lymphoma, while CAT was discovered during staging and clinical work-up of MALT lymphoma in the remaining 10 patients. All 13 patients had localized disease, i.e. stage I or II. Only one of the four patients with gastric MALT lymphoma responded to antibiotic treatment against Helicobacter pylori infection. Genetic aberrations were detected in four patients, two of whom had a t(11;18)(q21;q21) translocation, one patient had trisomies 3 and 18 and one had trisomy 18.

Our findings suggest that CAT is found in patients with not only thyroidal but also nonthyroidal MALT lymphoma. While the nature of our data does not allow for delineation of a direct association between CAT and development of extrathyroidal MALT lymphoma, further prospective studies on this issue are warranted.