Plasma cell granuloma of the thyroid.

We report two cases of thyroidal plasma cell granuloma. Both patients underwent surgical resection after presenting with painless neck swelling. Histopathologic examination of the specimens revealed plasmacytes infiltrating the thyroid parenchyma and immunohistochemical studies showed the polyclonal nature of the plasma cells. Plasma cell granuloma is a benign lesion and its appearance in the thyroid gland is extremely rare. Eleven prior cases with thyroid localization have been reported to date in the English literature. Nine of the plasma cell granuloma cases occurred in women, four in men (including the present cases). The clinicopathologic features and diagnostic difficulties of this rare entity are described, and its relation to inflammatory pseudotumor of other sites is discussed with a review of the literature.