Histologic features of autoimmune hepatitis: a critical appraisal.

We speculate that the "typical" histologic features (lymphoplasmacytic interface hepatitis, emperipolesis, and hepatocyte rosettes) of autoimmune hepatitis (AIH) are related to severity of hepatitis rather than etiology. We critically appraised various histologic features of AIH and compared them with cases of chronic hepatitis with similar inflammatory grade and fibrosis stage. Fifty-one patients with clinically confirmed AIH were identified at our institution, of which 43 biopsies (from 42 patients) were taken before initiation of therapy and formed the study group. Hepatitis C biopsies with similar grade and stage served as controls. Kupffer cell hyaline globules (KcHGs; P = .03), prominence of plasma cells in portal tracts (P = .003), "plasma-lymphocytic" inflammation (defined as plasma cells > lymphocytes), or as clusters (defined as ≥5) within portal tracts (P = .002) or lobules (P = .001) were significantly associated with AIH. Rosettes and emperipolesis lacked significance when controlled for inflammatory grade (rosettes, P = 1; emperipolesis, P = .4), supporting our hypothesis. Based on our findings, we developed a modified scoring system in which typical features require the presence of both (1) prominent plasma cells (plasma cells comprise ≥20% of inflammatory cells or presence of plasma cell clusters) and (2) KcHG. "Compatible" features include prominent plasma cells but lack KcHG, and "atypical" features include the presence of another disease process. Although application of this scoring system in our patients decreased the sensitivity to 77% (from 100%), it increased the specificity to 67% (from 0%). Further studies with different control groups are needed to validate these findings.