1. Department of Pathology and Laboratory Medicine, Section of Pathological Anatomy, University of Parma, Parma, Italy
2. Department of Digestive Diseases, 2nd School of Medicine, University La Sapienza. Rome, Italy
3. Department of Cell Biotechnology and Hematology, University La Sapienza. Rome, Italy
4. Digestive Disease Branch, National Institutes of Health, Bethesda, MD
5. Department of Pathology, National Cancer Institute, Bethesda, MD.
6. Biostatistics and Data Management Section, National Cancer Institute, Bethesda, MD.