Ultrastructural Findings in a case of Benign Lymphoepithelial Lesion (Sjögren's Syndrome)

Vascular endothelial cell participation in formation of lymphoepithelial lesions (epi-myoepithelial islands) in lymphoepithelial sialadenitis (benign lymphoepithelial lesion)

“…The presence of type-IV collagen in eosinophilic hyaline deposits has already been demonstrated by Palmer et al [27]. Ultrastructurally, hyaline materials were shown to have membranous or fibrillar structures with collagen characteristics [2,35] or to have a close association with the BM [5,19]. These hyaline materials were also considered to be immune complexes that originated from myoepithelial cells [28,35].…”

“…These cells were sometimes in the process of forming vessel walls but at other times were not yet assembled into blood vessels. Although the duct epithelial nature of their constituent cells has been well investigated by ultrastructural [2,5,9,11,19,28,32,35,40,41] and immunohistochemical [3,15,16,21,22,26,27,32,38] studies, there has been no postulation of endothelial cell participation in the formation of LELs. Only Qin et al [29] reported von Willebrand factor-immunopositive capillaries in the inflammatory stroma, suggesting that an efficient blood supply elucidates regeneration and proliferation of epithelial cells in the formation of the LELs in a general sense.…”

“…Lymphoepithelial sialadenitis (LESA [13], also referred to as benign lymphoepithelial lesion [2,9,40,41], lymphoepithelial lesion [3,5,18,27,30], myoepithelial sialadenitis (MESA) [10,11], Sögren-type sialadenitis [15], or autoimmune sialadenitis [21,22,32]) of the salivary glands is histologically characterized by an extensive infiltration of chronic inflammatory cells replacing the salivary parenchymal space, which is composed of acinar and ductal cells. In their full-grown stages, ductal cell remnants regenerate to form epimyoepithelial islands (EMIs), which sometimes show minimal ductal lumina but ultimately show solid epithelial nests.…”

“…In their full-grown stages, ductal cell remnants regenerate to form epimyoepithelial islands (EMIs), which sometimes show minimal ductal lumina but ultimately show solid epithelial nests. EMIs were first investigated using electron microscopy (EM) in the 1960s [2,5,9,11,19,28,32,35,40,41] and were shown to be composed of both duct epithelial and myoepithelial cells. However, immunohistochemical studies for cytoskeletal proteins were introduced in this lesion in the 1980s, which indicated that cells with duct epithelial characteristics are mainly responsible for the EMI formation [3,15,16,21,22,26,27,32,38].…”

“…However, this characteristic material has not been fully substantiated [2,5,21,27,28,35]. Recently, we have determined immunohistochemically that similar eosinophilic hyaline materials in adenomatoid odontogenic tumors (AOTs) are composed of enamel proteins as well as basement membrane (BM) molecules and that they might develop into the characteristic pseudocystic space formed by AOT cells with ameloblastic differentiation [25,33].…”