Fig. 2

Histological staging of NFMs. Histological observation revealed several stages of NFM. In the early exudative phase (stage I), fibrin deposition is apparent, as indicated by the bright red color in Masson trichrome staining (a) and confirmed by fibrin immunostaining (b). Podoplanin-positive fibroblasts are abundantly distributed in the encapsulating membrane (c). In the fibrotic phase (stage II), fibrosis is dominant, with many collagen fibers and sparsely distributed fibroblasts (d). In this stage, no fibrin deposition is detected immunohistochemically (e), whereas podoplanin is weakly positive in the fibroblast-like cells (f). In the scarring phase (stage III), the NFM is characterized by loose fibrous matrices covering the peritoneal surface, occasionally forming peritoneal adhesions with scant cellular components. Mesothelial cell coverage is observed on some areas of the peritoneal surface (g). Both fibrin (h) and podoplanin (i) were no longer detected in this phase. NFM staging was determined by the detection of fibrin and podoplanin by Masson trichrome staining or immunohistochemistry (j). All figures are ×200 and bars = 100 μm