A Histopathological and Electron Microscopical Study of Postoperative Maxillary Cyst

Abstract

Postoperative maxillary cyst (POMC) is a delayed complication many years after surgical intervention of the maxillary sinus. The present study performed histopathological and electron microscopical analyses of POMC in order to clarify the characteristic features associating with its pathogenesis. Histopathologically, various types of epithelial cells lining the cysts were frequently observed. The combination of squamous, columnar or cuboidal epithelium with or without cilia was most major (40 cases, 67%) following by columnar (8 cases, 13%), squamous (7 cases, 12%) and cuboidal epithelium (4 cases, 7%). A case of non-epithelial lining (1%) was also identified. The lamina propria consisted of fibrous connective tissue showing various histopathological changes. Fibrosis, almost including hyalinization, was the most frequent change, 25 cases, 41%, following by mixed changes of fibrosis, inflammatory cell infiltration or edema (24 cases, 40%), inflammatory cell infiltration (7 cases, 12%) and edema (4 cases, 7%). Electron microscopically, the ciliary cells showed 9 + 2 pattern as a typical feature of the respiratory epithelial cells, whereas abnormal features in ciliary cells comprising of absence of central microtubles and irregular arrangement of peripheral microtubles were identified in advance lesions. The basal lamina was swollen and thickened. A tendency of anchoring fibrils to disappear was noticed. Lamina propria consisted of densely accumulation of collagen bundles but sometimes the bundles were sparsely observed. The results suggested that the pathogenesis and growth of POMC had relationship with epithelial degeneration, hyalinization of the lamia propria and thickened basal membrane as regressive changes, edema, retention of the involvements, inflammatory cell infiltration, proliferation and dilatation of the capillary vessels as peripheral circulation disorders, relining and proliferation of the epithelium, squamous metaplasia and fibrosis as progressive changes after surgical operation of maxillary sinusitis as an iatrogenic disorder.