Glomeruloid peritoneal implants in ovarian serous borderline tumours - Distinction between invasive and non-invasive implants and pathogenesis

Aims: To determine whether or not the glomeruloid implants (GI) composed of papillary cores within clear spaces lined by mesothelial cells or tumour cells located in superficial or deep peritoneal tissue in ovarian serous borderline tumours (SBTs) are invasive. Methods and results: We examined the differences in incidence, histological and immunohistochemical findings among three groups: 100 GI with mesothelial cells lining clear space (type I), 100 GI with tumour cells lining clear space (type II), and 100 invasive implants with clefts but no lining cells from 30 cases of SBT with peritoneal implants. The type I lesion had characteristics of non-invasive implants with a tendency for smooth contours (100100), superficial location (71100), absence of desmoplasia (100100) and absence of surrounding destructive invasion (100100), In contrast, type II GI had irregular contours (67100), deep location (93100), presence of desmoplastic reaction (100100) and presence of destructive invasion (12100). Immunohistological studies suggested intermediate forms between the two types of lesions. Conclusions: Type I GI are non-invasive implants, whereas type II GI are invasive implants and it is important to evaluate the presence and nature of cells lining the clear space in determining whether implants associated with ovarian SBTs are invasive or not.