Thymus - Ectopic Tissue
comment:Ectopic tissue is a fragment of structurally normal tissue (e.g., thyroid, parathyroid) in an abnormal location. This lesion can be congenital or the result of an injury. Ectopic thyroid tissue may occur in and/or adjacent to the thymus of rodents. The thyroid tissue shown in Figure 1 consists of epithelial-lined, colloid-containing follicles separated by a fine fibrovascular stroma. Thyroid C cells may occasionally be found between the follicular epithelium and the basement membrane of the thyroid follicles. Ectopic parathyroid tissue occasionally occurs either adjacent to or embedded in the thymic capsule of rats and/or mice. The parathyroid tissue shown in Figure 2 consists of densely packed, highly folded, branching cords and clusters of polygonal cells separated by a thin fibrovascular stroma. Ectopic parathyroid tissue is an uncommon, incidental finding, although when present it should be distinguished from thymoma or other possible early or small tumors.
recommendation:Ectopic tissue is typically an incidental finding in or adjacent to the thymus of rodents. When this lesion is present it should diagnosed but not graded. The type of ectopic tissue present (e.g., thyroid, parathyroid) should be included in the diagnosis as a modifier (e.g., Thymus - Ectopic tissue, Thyroid).
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Web page last updated on: February 03, 2015