Lipid-rich residual bodies in the human thyroid gland: ultrastructural, histochemical, and morphometric study.

Abstract

Eleven samples of surgical and autopsy thyroid tissue were studied by classical histology, histochemistry, immunohistochemistry, light microscope quantitation and transmission electron microscopy in order to characterize lipid-rich residual bodies (LRRBs) previously reported in human myometrium. The following observations were made: 1) LRRBs were found largely in follicular epithelial cells; 2) they had exactly the same histochemical, immunohistochemical and ultrastructural characteristics as LRRBs from myometrium; 3) they had a distinctive distribution and morphology compared with lipofuscin; 4) a lysosomal nature was confirmed by their content of acid phosphatase and cathepsin D; 5) they were virtually absent from both the new-born thyroid and from thyroid carcinoma; 6) there was a statistical linear correlation between LRRB frequency and patient age. In conclusion, LRRBs have been demonstrated in an extra-uterine location, and are confirmed as residual lysosomes, probably having been involved in lipid metabolism.