RESUMO
<p><b>OBJECTIVE</b>To analyze the ultrastructural characteristics of ectopic endometrium in endometriosis.</p><p><b>METHODS</b>Ectopic endometria collected from patients with adenomyosis and ovarian endometriosis were examined under transmission electron microscope (TEM).</p><p><b>RESULTS</b>In comparison to normal human endometrium, the ectopic glandular epithelium of adenomyosis patients showed reduced and shortened microvilli covering the surface of the secretory cells, with obviously increased, elongated and irregularly aligned cilia of ciliated cells projecting into the lumen. Numerous microvilli and cilia broke off from the cell surface and shed into the lumen. The mitochondria were enlarged, and multiple polyribosomes were present on the surface of RER. The Golgi apparatus with electron-lucent vacuoles was seen frequently. The glandular cells contained many lysosomes, lipofuscins and myelinosomes, and the cell nuclei showed varying shape and size. The nuclear membrane of the epithelial cells was irregularity. Cytoplasm protrusion containing a few organelles occurred and shed into the lumen. Some ectopic epithelial cells showed characteristic features of necrosis. The basement membrane became markedly tortuous and focal lysis of the extracellular matrix was seen. Ultrastructurally, the ectopic glandular epithelium in ovarian endometriosis showed short and sparse microvilli on the free surface of the secretory cells. Some microvilli broke off from the surface. The short cilia of the ciliated cells were seldom seen. The mitochondria were enlarged. The glandular cells contained small amounts of RER, many free ribosomes, Golgi apparatus, lipofuscins and myelinosomes. The nuclear membrane showed obvious irregularity. Some ectopic epithelial cells had giant nuclei. Cytoplasmic protrusions containing small amounts of organelles were observed in some ectopic epithelial cells. Apoptotic cell death occurred in some ectopic glandular epithelium cells. The basement membrane became markedly tortuous, and the decidual-like cells containing abundant short and club-shaped RER were observed. The number of macrophages was obviously increased.</p><p><b>CONCLUSION</b>The ultrastructural change of the ectopic glandular epithelium in endometriosis promotes its transformation into endometriotic lesions.</p>