A Histopathological and Immunohistochemical Study of Vascular Localization on Schwannoma in the Oro-maxillofacial Region

Abstract

Schwannoma is a relatively rare, benign peripheral nerve sheath tumor that affects the oro-maxillofacial region. The peripheral nerve tissues are known to be closely related to vascular tissues from viewpoints of morphology and physiology. Therefore, the authors speculate that schwannoma of peripheral nerve origin is also associated with vascular tissues ; however, the histogenesis with regard to vasculature is not fully understood. The authors investigated the localization of the blood and lymphatic vessels in schwannoma using histopathological and immunohistochemical methodologies. The tumor parenchyma consisted of a proliferation of relatively long spindle cells with nuclear palisading (Antoni A type), diffuse spreading with myxoid or edematous background (Antoni B type), and encapsulation with fibrous tissue (capsular tissue). In one case, the tumor exhibited multicystic growth. Dilation and hyperplasia of the vessels were observed in the Antoni A and B zones, the border of the Antoni A and B zones (border zone), and capsular tissue. With periodic acid-Schiff reaction-alcian blue pH2.5 staining, the myxoid matrix in the Antoni B zone was stained blue. Immunohistochemically, CD-34-positive blood vessels were found in all cases. The vessels were predominantly observed in the Antoni B zone, and only moderately in the Antoni A zone, border zone, and capsular tissue. Four cases showed that D2-40-positive lymphatic vessels were mainly observed in the Antoni B zone and capsular tissue, and only moderately in the Antoni A zone. In the other four cases, D2-40-positive lymphatic vessels were only indicated in the capsular tissue. In addition, positive immunoreactivity for D2-40 was found in the cyst-lining cells in the multicystic case. Microvessel density (MVD, numbers of blood vessels per unit area) was calculated for CD-34-positive blood vessels. MVD was 3.4±2.1 in the Antoni A zone, 6.0±1.7 in the border zone, 9.4±3.2 in the Antoni B zone, and 2.7±1.0 in the capsular tissue. In addition, lymphatic vessel density (LVD, numbers of lymphatic vessels per unit area) was calculated for D2-40-positive vessels. LVD was 0.2±0.5 in the Antoni A zone, 2.7±3.5 in the Antoni B zone, and 2.4±0.9 in the capsular tissue. These results suggest that the localization of the blood and lymphatic vessels was closely associated with the histogenesis of the Antoni B zone in schwannoma, not only by the degeneration and over-expression of the myxoid matrix but also by the edematous change from circulation disturbance in the tumor tissues during benign tumor growth and development.