Patterns of basement membrane deposition in benign, premalignant, and malignant endometrium

Immunocytochemical staining for laminin, an intrinsic basement membrane component, was used to show and quantify the distribution of basement membranes in endometrium. In normal endometrium, glands which are not mechanically disrupted have almost entirely continuous basement membranes, even in the menstrual phase. This is also seen in benign cystic hyperplasia. In atypical hyperplasia a small proportion of glands show small breaks in basement membrane staining in the absence of invasion. The number of breaks increases with more severe cytological changes, and this abnormality may persist even when a second biopsy specimen shows an apparent return to normal morphology. Invasive tumours show a strikingly different pattern of basement membrane staining, even when very well differentiated.