Histology of the normal thymus.

We present a review of the normal histology of the thymus, with special emphasis on the developmental, morphologic, and immunohistochemical aspects pertinent to the interpretation of thymic lesions in surgical pathology. Attention is drawn to normal variations in histology, embryonal vestiges and developmental defects, involutional and hyperplastic changes, tissue reactions to injury, and biopsy artifacts that may constitute a source of diagnostic problems.