Hashimoto Thyroiditis & MALT Lymphoma

Comments:
Hashimoto Thyroiditis & Thyroid Lymphomas: Hashimoto thyroiditis is usually seen in adults (median age 60) with a marked female predominance. It can also occur in children in whom it accounts for many cases of pediatric goiters.

Patients form anti-microscomal (95% of cases) and anti-thyroglobulin antibodies (60% of cases). Other autoimmune disorders may also develop. The breakdown of immune tolerance involves both humoral and cellular mechanisms. The inciting event is cell injury possibly caused by infection (bacterial or viral), toxins, or unknown agents. The injured thyroid cells expose new epitopes, causing influx of antigen presenting cells, clonal expansion of autoreactive T-cells, and IgG producing B-cells.

Microscopically, Hashimoto thyroiditis shows marked damage to the thyroid parenchyma with lymphocytic infiltration of the gland and formation of large lymphoid follicles with well-demarcated germinal centers. The thyroid follicles are small and atrophic and the follicular cells show prominent oxyphilic (Hurthle cell) change.