Abstract

Carcinoma Showing Thymus-Like Differentiation (CASTLE) is a rare tumor, which occurs in the thyroid gland and surrounding soft tissue, or soft tissue of the neck. It is thought to originate from ectopic thymus or branchial pouch remnants. We report a case of CASTLE of the thyroid gland in a 42-year-old woman. Grossly, a nodular, partly well demarcated, grayish yellow, 3.0 2.0 cm sized, solid mass was found in the right thyroid gland. Microscopically, the tumor was divided into lobules of variable size and shape, nests and cords with thin and thick fibrous septa which were infiltrated by lymphocytes and plasma cells. The tumor cells were large, polygonal and had vesicular nuclei with prominent nucleoli and eosinophilic cytoplasm. Some cells, especially in the central portion of the nests had abundant eosinophilic cytoplasm and showed squamoid feature.

• Keywords: CASTLE;Thyroid gland