Basement membrane proteins, apolipoprotein E and glycosaminoglycans in pituitary adenomas and their correlation to amyloid.

The aim of the study was to confirm earlier reports of the association of amyloid deposits in growth hormone (GH)-producing adenomas of the pituitary and the presence of glycosaminoglycans, basement membrane proteins and apolipoprotein E (apo E). Serial sections from 17 amyloidotic and 11 nonamyloidotic, sparsely granulated, GH-producing adenomas obtained from patients presenting with acromegaly were stained with Congo red and Alcian blue, and also with antisera directed against fibronectin, collagen IV, laminin and apo E. Glycosaminoglycans were found in capillaries of every adenoma and were also related spatially to amyloid deposits. Immunostaining of both nonamyloidotic and amyloidotic adenomas demonstrated the presence of fibronectin, collagen IV and laminin in the basement membranes of surrounding nonadenomatous tissue and tumour vessels. In approximately half the amyloidotic adenomas, each basement membrane protein presented with a distinct spatial relationship to amyloid deposits. Apo E was found in 88% of the amyloidotic adenomas within the amyloid deposits, and in six cases intracellular immunostaining was also evident in folliculo-stellate cells. The results are consistent with the presence of glycosaminoglycans, basement membrane proteins and apo E in the amyloid deposits of pituitary adenomas.