Fibronectin in basal cell epithelioma: sources and significance

Nodular basal cell epitheliomas (BCE) contain fibronectin both within tumor nodules and at the nodule-stroma interface (basement membrane zone). Fibronectin within or at the periphery of tumor nodules could be derived from the tumor cells, from entrapped stroma, or from plasma. The present study was designed to elucidate the source(s) of fibronectin within BCE nodules. If stromal entrapment occurred to any great extent, von Willebrand factor VIII:Ag-stained blood vessels within tumor nodules should be evident by immunofluorescence techniques. Likewise, if plasma proteins were deposited in BCE, the tumor nodules should stain with fluorescein-conjugated antifibrinogen antibodies. Therefore, 6 basal cell epitheliomas were double labeled with rhodamine-conjugated antihuman fibronectin and fluorescein-conjugated antihuman factor VIII:Ag or fluorescein-labeled antihuman fibrinogen. Fibronectin was present in a linear disposition along the margin of tumor lobules and as a fine filamentous deposit in the central portions of tumor tissue. There was no evidence of fibrinogen or factor VIII:Ag in any of the tumor lobules. Factor VIII:Ag was present in a granular pattern within blood vessel walls that coursed between tumor nests. An indirect immunoperoxidase technique using rabbit antihuman fibronectin and peroxidase-labeled goat antirabbit IgG demonstrated that fibronectin within the central portion of the tumor lobules was closely associated with the tumor cells. The absence of fibrinogen and factor VIII:Ag within the tumor tissue indicates that the fibronectin is probably not plasma- or stroma-derived while immunoperoxidase data suggest that fibronectin may be a product of BCE cells.