1. Method for diagnosing “in vitro” abnormal morphological conditions in human or animal tissues affected by a chronic inflammatory disease, which comprises observing an image of a biopsy sample of the human or animal body in which said abnormal condition can be detected and metrically quantifying said abnormal morphological condition, wherein said step of metrically quantifying comprises detecting the extent of the fibrotic and of the inflammatory tissue by means of: i) calculating the fractal corrected perimeter (Pf) and/or area (Af) of the collagen islets, and ii) calculating the percentage area of the clustered inflammatory cells by means of the formula A CINF /A B ·100, wherein A CINF is the actual area of the inflammatory cells belonging to clusters and A B is the area of the biopsy sample.