The extent of basement membrane confinement among 5 cases of
ameloblastoma and a malignant counterpart were studied by immunohistochemistry. For these studies,
antibodies to 2 basement membrane components,
Type IV collagen and
laminin, were studied by immunohistochemistry. Our results show that the
tumor islands of
ameloblastomas are circumferentially delineated by a linear staining to both antibasement membrane
antibodies, and that these findings were consistent for all of the patterns of
ameloblastoma investigated. These data suggest that
ameloblastomas spread into tissue spaces by expanding their compartmental volumes rather than by secreting
proteinases that disrupt their basement membranes compartmental barriers. In contrast, the single case of malignant
ameloblastoma investigated was not delineated by circumferential linear basement membrane components. However, this
tumor and all of its
metastases did contain numerous focal areas of
Type IV collagen and
laminin immunoreactive materials. Collectively, these studies indicate that the use of specific
antibodies to basement membrane components may help to differentiate
ameloblastomas from malignant lesions.