[580] A Comparative Histopathological Evaluation between Subgroups of Hashimoto's Thyroiditis.

Yaqiong Li, Zhiyan Liu, Takashi Ozaki, Emiko Taniguchi, Ichiro Mori, Kennichi Kakudo. Wakayama Medical University, Japan

Background: Hashimoto's thyroiditis (HT) is commonly considered as a well-defined clinicopathological entity. Its diagnosis and treatment have changed little over the last few decades. We herein describe a subsection of HT characterized histologically by dense lymphoplasmacytic infiltrate, stromal fibrosis, large numbers of IgG4-positive plasma cells, and serologically by elevated IgG4 titer. These cases seem to represent a distinct form of HT and have close relationship with IgG4-related sclerosing disease.
Design: 114 cases of surgical samples from patients with HT were involved in this study. Immunostaining of IgG4 and IgG was performed on paraffin sections and the histopathological characterisitics of these cases were evaluated.
Results: On the basis of immunohistochemistry of IgG4 and IgG4/IgG ratio, the 114 patients with HT were divided into two groups: IgG4 thyroiditis (33 cases) [figure1A] and non-IgG4 thyroiditis (81 cases).

Histopathologically, IgG4 thyroiditis [figure1B] showed higher grade of stromal fibrosis, lymphoplasmacytic infiltration and follicular cell degeneration than non-IgG4 thyroiditis. In addition, before operation, serum IgG4 concentrations were significantly higher in IgG4 thyroiditis than non-IgG4 thyroiditis. After operation, the serum IgG4 levels of patients with IgG4 thyroiditis decreased significantly. Furthermore, IgG4 thyroiditis and non-IgG4 thyroiditis present different clinical features, with IgG4 thyroiditis being more closely associated with rapid progress, subclinical hypothyroidism, higher levels of circulating antibodies, and more diffuse low echogenicity. No other organs were found to be involved by IgG4-related sclerosing disease in this patients' series.
Conclusions: Hashimoto's thyroiditis can be subclassified into two groups, in regard of IgG4-positive plasma cell population: IgG4 thyroiditis and non-IgG4 thyroiditis. IgG4-positive plasma cell infiltrate is a marker of fibrotic variant of Hashimoto's thyroiditis, which shows atrophy of follicles and stromal fibrosis, resulting in subclinical hypothyroidism more. New insights into HT with special reference of IgG4-positive plasma cells offer a novel way of viewing this well-defined disease.
Category: Endocrine

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 79, Monday Morning


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